Having Hep C and drinking alcohol is like pouring gasoline on a fire. It's a very bad situation.
Her doctor is wrong. There's only a 50% cure rate - not 90%. Jacker is right. Go over to the Hep C forum and educate yourself so you can help her.
Good Luck.
Tell her to go on the Hep C forum, or you might want to go on there yourself. People who have Hep C and also continue to drink have an alarming rate of liver cirrhosis. That's not a desease I'd wish on anyone.
There's also a site I know that has a cirrhosis forum and many of these people have Hep C - it's an education. It's on ****.***. I spelled it that way because I don't think we can link to other sites from med help. If she talks with some people on this forum, it may change her mindset.
You can try Al-anon from what I've heard that's a support system for famly members of people who continue to drink... Otherwise there isn't much, but prayer I guess. I'm sure people who know more will be able to offer their advice.