AITAH for pouring my mothers drink down the sink?

Im 17F and my mother is 48. My mother has always been a drinker. She would get drink often and ive asked her many times over the years to stop and she didn't.

This year, she got drunk on my birthday and ruined the evening because she gets really crabby when shes drunk. I got really mad at her that day. She agreed to only drink on weekends. She asked if she could drink on friday evenings too, I said yes, even if I didn't really want her to.

She's under a lot of stress taking care of my grandparents and I dont want her to not be able to relax. But I also worry about her health, because overtime I can see her drunken state getting worse. She takes all these healthy minerals and vitamins to stay healthy but I never understood the point if she drank so much? Idk.

Anyway, today I went up to visit her at my grannies house around 4pm and I saw she had a gin and tonic out. When i walked back in, she had put it away. I looked in the fridge and it was there but it felt like she kept trying to close it on me. I got annoyed and I poured it down the sink when she wasn't looking.

I feel awful because I forgot that we had agreed friday evenings, and i honestly know i'm the asshole already. Im only writing this to make myself feel better which is horrible of me.

I just got angry and need advice how to stop being angry even though shes a grown woman and shes allowed to drink.