Need Advice!!

I have this friend whom I’ve known for awhile now and she’s always been this really good, innocent, never does anything wrong type of person. Now that she’s 21 though she drinks a lot and gets drunk all of the time. I’m afraid she might turn into an alcoholic and other people think so to. She however of course denies that. She says she just likes to have a good time. She drinks waaay too much thought. I don’t really know what to do because I already have other friends who have gotten really sick from drinking too much. I have one friend with a liver disease and one who’s liver is half dead and doesn’t work. She needs a transplant and because she’s like number 200,000 and something she has to keep going to the doctors to try and stay healthy. She’s going to miss the first month or two of school this next semester because she has to go to another city to go to the doctors and she missed a month last semester from being in the hospital. And my other friend who has the liver disease is always in pain and hurting a lot. I don’t want my other friend to go through this stuff too. And I also don’t want her to harm anyone else either. She can get kind of violent when she’s drunk. I just don’t know what to do though. It’s hard helping someone who doesn’t think they have a problem.