Sick grandparent(s) moved in and are now inciting anger and stress

it seems like you care about your mother so I would recommend helping her out and trying to ease her in this situation as much as possible (as much as you care).

It seems to me like there can't be done too much about your grandma so if you care you can try helping her out somehow, if you don't care about her you should try getting her out of the house (that's what I would do) - she is not happy anyway and she poisons rest of the family, she also seems not to be sane so reasoning won't work.

Talk to your dad and mom about the problem - that's for sure.

I am coming from a different cultural background (US), but I was in a similar experience with my family. My paternal grandmother moved in with us (mom, dad, me) because of her failing health. Both of my parents were retired, but because of the division of labor in the household, my mother wound up doing much of the care giving. I could act as a buffer for a few years but when I went to college things fell apart and my parents divorced. Now my grandmother and father live together and are both miserable.

The other answer focuses on acting as a buffer, and that is something you will have to do, but understand that it is only a short term solution. It is hard to predict how long your grandmother may live with you/your parents. It could easily be the next 20 years. You can't be expected to live at home that whole time, and your mother can't be expected to put up with being miserable for that long.

Some things that help are getting your grandmother out of the house and active, and getting her therapy/treatment for any mental anguish arising from the situation.

For your grandmother helping around the house is a way of staying active, being helpful, and retaining normalcy since that is probably what she did in her own home. As long as it is not a safety problem, then let her do those things. Give her a responsibility. We let my grandmother do the dishes. So she has something to do, but stays out of the way when cooking is going on. You could let her do the dusting, but not let her do anything in the kitchen. Give her something useful to do that keeps her away from your mother when she is doing something that could be criticized.

Does your grandmother have any friends or other relatives nearby who could visit or take her out for a day? If she is cooped up all day with nothing to think about but the ill health of her husband, then she will have nothing better to do than bother your mother. Mental stimulation is important, not just as a distraction, but also as a way of staving off dementia and depression.

With my grandmother, when she stopped having people who could visit, that is when she started declining mentally and became mean. Dementia and depression are common in the elderly and need to be treated. A therapist could help her deal with the grief of losing her husband, and if they think it is appropriate, some medicine could help improve her mood. Culturally, this may not be acceptable in your household, but in mine it did help somewhat.

The biggest pain point from my mother's end was that through all of the health problems and worsening mood of my grandmother, she had no help. I was like you, in school/work all day and trying to relax at night. My father was retired but had other activities that had him out of the house most of the time. She was the one who had to clean up, cook, and talk to my grandmother all day. It seems your situation is less flexible since your dad works so much. But perhaps there is a compromise. You could cook a couple nights a week. He could take his mother out when he has a free day. You could take her out when you have a free day. Somehow reduce the workload and exposure for your mother. Does your mother have friends? Make her go on a "girls night out" to relax and get out of the house.

You could try to arrange a meeting with your parents and honestly discuss the situation. I think recording the incidents would result in an argument, so perhaps don't bring that up, but everyone should voice their concerns and suggest ways to improve the situation. Even though your family didn't do this kind of thing before, you have to do it now, before tempers get too high to talk and fix the problem.

This answer is highly dependent on you. Your schedule, your life, what you do, how much are you around the family in any given day; you could be an excellent shield here and that won't be possible if you cannot be around enough.

My mom has an 88-year old uncle and his 79-year old wife. I just call them grandma and grandpa because it is easier and we don't have very specific terms for our relations where I am from (India). It is usually just made simpler with a very generic term.

My "grandpa" is deaf, or actually, gone deaf. My grandma is incredibly passive aggressive and lazy and cheap. Not badmouthing the elderly, but that is just how she has always been. She is so self-centered, she acts like she's deaf too. She intentionally acts like she doesn't hear you talk. But when my mom says something that my grandma likes, like money, or food, or jewelry, she can hear better than a bat. But if it is about doing something or buying something, she will just keep saying "whaatt??".

My mom works. My dad is retired and my uncle (my dad's younger brother) lives with us. Who gets to deal with this fun couple? My dad and uncle.

Obviously, it is cruel to not help these people out when they've helped my mom when she was little. They are old and incapable of doing much on their own, so there isn't much you can expect of them. They're scared and lonely almost all their time. My grandma keeps talking to herself about what she is going to do when her husband dies. It is sad to watch her mumbling to herself. The grandpa on the other hand was a very athletic person when he was young but now has horrible legs and hearing and eyesight, so that is sad too.

How does my dad and my uncle put up with it every day? They actually don't. All they can do is what is expected of them. They cannot be rude, or mean, or disrespectful. But if they have to keep putting up with this, they'd blow their brains out. So when I used to live with them and "grandparents" visited, this is what I used to do.

1. Sit with them and talk to them.
2. Help around the house.
3. Take them outside the house.
4. Turn the TV on and let them just sit there and watch their TV shows (of course it has to be at a thousand volume for my deaf grandpa, but it is better than being badmouthed and treated like a slave by my grandma).

Basically just distract them from driving everyone else in the house nuts. I was 22 when this last happened and I had to be a cushion between my grandparents and my parents. They are so old that in perspective, I was like a child to them. I was always joking around, making them laugh, just generally happy about being alive.

I think that a good bit of the responsibility on keeping things calm falls upon you. As you mentioned, the grandma does not treat your mom badly when you're around, so you be around more. You try to help your mom. You joke around. I know this is a very difficult time for the family and your grandma, but that doesn't mean everyone needs to be in a grumpy mood all the time. You can sit down and talk stories about grandma and grandpa's past, make her feel warm inside.

To answer your specific questions:

1. Is this within the extent of what needs to be tolerated from and older person?

That is completely up to each individual person. Culture plays an important part in this too. But generally, no. You don't need to tolerate this much. But you can choose not to by not having anything to tolerate. That is what, in my opinion, your goal should be. To reduce the amount of stress thrown your way, not to keep dodging all the stress.

2. What could I do to stop grandma from constantly venting to and taking her sadness out on my mom?

Help her take her sadness out on purely the fact that there is sadness in her heart. Help her cope better with this situation and express purely sadness rather than frustrated passive aggressive comments and gossips about your mom and your dad's sister. The best way to do it, as I mentioned earlier, is to reminisce about her past with grandpa. To talk about their fun young times. Make her sad with nostalgia rather than sad and stressed out about how that is all going to be over soon.

3. Is there any advice I could give my mom on how to avoid the stress that comes with the situation?

I feel like your mom could be more understanding of your grandma's pain and act a bit differently that would benefit both of them. Like this sentence right here:

"I'm working on it, I cannot cook it any faster"

I cannot cook any faster sounds arrogant and mean (even though she didn't mean it to be). That would make your grandma feel unwelcome in your house. Especially a grandma who is in a lot of pain emotionally. She could rephrase her sentence to something like:

"Almost done, give me a few more minutes"

When your mom told your grandma that she won't be awake to let her in, did she finish the sentence with:

But don't worry my daughter will be awake and she can let you in.

? If she did, good. But if she didn't, she needs to. You could suggest your mom covers ALL HER BASES whenever she says anything to her. Take the extra effort to sound pleasant and sweet.

I know this is not an easy phase for your mom to be going through either, but your mom should be able to change her attitude towards this whole situation a lot easier than your grandma can, given her age, her emotional situation, and her health.

Conclusion:

Please remember, secretly recording your grandma saying mean stuff to your mom and playing it to your dad is not going to help you in any way. That could backfire heavily in regards to "being insensitive about grandma's difficult time". Maybe your dad talks to your grandma, maybe he gets upset about grandma's behavior, the end result would eventually not be satisfactory to your mom.

If your grandma insists on helping your mom just so she can use that time with her to vent, you take her away from the situation. Tell her you'd really like it if she'd sit down and talk to you instead of struggle around the house trying to help. If she is venting to you and being mean to you, it does not really matter. The fact that you wanted to find out what you can do to alleviate this situation in itself shows maturity on your part and you should be able to take some venting. Its at least not your mom and that is what is important.

I hope this helps you help your mom be more relaxed and happy. I also hope your grandparents go through this difficult time of their lives with ease.