AITA for not helping my drunk sister after arguing with her?

I (F21) have a younger sister (F18) and we got into an argument between Christmas and New Year’s Day as we often do.

I was very upset during dinner and cried for a personal reason and she later accused me of ruining the vibe, wanting attention etc which deeply hurt me because she never once made an attempt to even ask what’s up and straight up got pissed.

In return I got pissed as well and it kind of escalated, she forced me to apologize and I did, but I was still hurt because from her side there was never an apology.

Well a few days later it’s New Years Day and we’re having a party with friends. They brought some strong alcohol (We’re from Europe so the drinking age is lower). I already know my tolerance and I can’t stand alcohol so I decided to stay sober.

I told her to also be careful and warned her of feeling shitty in the morning because that’s my experience too.

She has drunk before as well but never that much, she was cheerful then but this time it really made her feel miserable. It wasn’t blackout, she didn’t throw up or become unconscious but just started crying, sobbing and complaining how awful she felt, with our mother offering her some help by letting her lay down, giving her fresh air and just comforting her.

But honestly I myself didn’t feel much empathy, especially because I kept telling her that alcohol isn’t fun and this is what I think makes me an asshole. Because I just left my mother alone with my sister (it happened in the basement of our house so I just went upstairs) and said I don’t want to deal with this right now, she did this to herself and she has never comforted me whenever I was sad over things I couldn’t control.

None of my family explicitly told me to stay, as I said it’s not a life or death situation. I just didn’t feel like dealing with her after she forced me to apologize and ignored my warnings about drinking too much. Does that make me an asshole?