I donated my mother's library books to charity without telling her
That is not good. Were they books that they wanted?
It was mostly old and unwanted books that took up space in my house.
I mean, if they were in your house and just taking up space, I don't see the issue here. If you promised her you'd keep them safe or something similar, then that's a problem.
Yeah but I don't care.
You should have a little bit more guilt for what you did depending on what you told your mom about storing her books. I hope maybe in time you can be honest with her about it.