Fantasy Novel/Series: Purple/Violet Eyes, Reincarnation, Battle?

I may have gotten a few things mixed up, but the parts I remember for sure:

• the book starts with a female character "plucking" a male human (a knight/soldier) from his time into her world, because she needs him (to lead a battle? save her world?)
• they need to have sex three times (before the sun rises? the night ends?) in order for him to stay in her world
• the female has unique coloured eyes (purple/violet, if I remember correctly)
• taking the man from his time/world into hers is considered "wrong" and so she must pay the price by being reincarnated in the human world (five times, I think)
• the epilogue mentions a(n indigenous) father showing his new daughter the sunrise, and the baby has the same unique coloured eyes as the female character

There is a sequel where another female character does the same thing ("pluck" a human male from his time; I think he was a soldier fighting in a Spanish war or something) but she happened to drink from a fountain/lake or something beforehand, and she wasn’t punished with reincarnation. Other characters analyse this and suggest the water might have something to do with it. The first female character returns to their world after completing her punishment…there’s a mention of one of her reincarnations where she was a mother in the human world and she tried to breastfeed her baby, but she realised the child had already died.

I read this book over 15 years ago, if I remember correctly, so it was likely published before 2005.

One thing I’m not so sure about…this might be from a different book and my memories may have gotten muddled: the original female character has a talking, sentient dog as a companion. He remains in their world, waiting with the male human for her return while she completes her punishment. In the sequel, other characters mention that the dog has aged/is getting old.