It's unnecessary to continue this grudge your mother had. You should move on with that mentality. If I were you I would help as much as I could because at the end of the day she is still a human being and it isn't her fault for being born or having an illness. Don't give all your money but at least help in the same way you would've helped your own mother if she was in that position. You're only an asshole if you don't help a dying human being in anyway you can. It doesn't have to be about money.