I went round to my parents house last night and my sister got really drunk in her room and was throwing up. When she had finished being sick she came into the kitchen and wanted to open a bottle of vodka, my brother tried to stop her but she became very aggressive and told him she'd put him over her knee if he didn't give it her back. My parents made him give it to her because its hers and she went back into her room presumabley to get hammered again. She regulary gets drunk alone (2-3 times a week) since she broke up with her boyfriend and moved back in with my parents. My parents say that she is 25 and she buys it so there is nothing they can do (I think they are in denial), and my brother seems worried but he's only 16.
She is destroying her health and her life, AIBU to be very worried and to want to step in and try to help her to stop drinking. DP says its pointless if she doesn't want to help herself.