She is in 12th standard, and having a group of friends who go out for partying regularly. My parents have been liberal with me, so are they with her. She used to go for tutions (as she told us) wth her friends, and we never came to know till in the last month, that they have been missing classes in the maths tution regularly for about 7 months or so. Since there had been no complaint from school regarding her studies, we never showed any over-curiosity about her private space. After the revelation, my parents were really angry, and didn't want her to go out anymore with anyone. But she is behaving abnormally, she is getting violent, frustrated sometimes and so aggressive that we fear she will destroy things or hit someone.
When I spoke to a couple of friends she has been hanging around, they informed that she is into drinking regularly with the group in the parties; I never realised this thing, when she came back, but it is true they say. My sister is now getting really restless to go out with her friends, sometimes, she even tells me that she wants to drink and that I bring it to her. I believe she is addicted, she is very young and I am really worried. How can I help her?