Depressed budgie

Budgies live for 5-10 years in captivity.

From the Pittwater Animal Hospital in Australia:

On average, the life span of budgerigars is about eight years, but some live longer than twice that.

She is getting old for a budgie. Also depending on how old she was when you got her, she may be older.

The other thing to do is ensure all her nutritional needs are met. In many cases, for any animal including humans, nutritional deficiencies can take time to show symptoms.

Ensure your birds have cuttlefish, some access to some type of green grass. Growing some of your bird seed in moist tissue paper is good for supplying green peck. Also provide grit along the bottom of the cage for the budgies - this is now a controversial issue surrounding budgie ownership. As someone who grew up with budgies, and in the land where they are native, providing grit has always been considered beneficial and budgies will eat small amounts of grit in the wild. Be sure the grit has both soluble and insolube components.

From the Pittwater Animal Hospital in Australia:

In their natural habitat, budgerigars are mostly vegetarians, feeding on grass seeds, eucalypt leaves, buds, bark and other greens. On occasion pet budgies can be given cooked chicken bones and boiled eggs to increase their protein intake. Because such foods tend to go off quickly, they should not be left in the cage any longer than a day.

Maybe the surrounding area of the budgie is becoming noisy or uncomfortable for the budgie. To prevent that maybe try tidying the area up or letting her fly around the house With the windows closed and curtains pulled over so that she can fly around a bit freely. This may help.

I am also a parrot owner and I will try to help you out. First off, birds can become depressed in many ways. So it will probably be difficult to figure out what is causing them to be depressed. If you cannot figure out why, I recommend you take your bird to an avian vet for a check up. Birds could change personality because of sickness. In the meanwhile, you should spend more than 4 hours a day with your bird. Let the bird spend some time out of the cage so it can get some space to exercise. Check your environment of where the cage is located. Birds could easily get stressed because of its surroundings. I will put a link to a website that goes over some advice that I have mentioned. Check out this website: https://pets.thenest.com/calm-parakeet-7342.html