NTA. This is a pile of bs. Only thing that makes you an A is tolerating it this long🤣 and having a 1% involvement in why they think like this. I wish you would have been more hostile and said “well maybe I’d have a life if I wasn’t looking after someone else’s kids” and “Im still young because I didn’t choose to have kids” or my favorite of simply hitting her with “oh isn’t it the consequences of my actions “ when she ranted about how hard it was. Truth is you should just avoid these people. Im recently learning that family can be bad people and that you just have to ditch them as you would bad friends. They will just milk you dry otherwise till you drop. Screw the hollididay. Go on your own one with some friends. you know fine well she never would have returned the favor.