Hi Friend,
I'm sorry about this development and your friend clearly needs help. But, you do not need to talk to either of her parents if you are not comfortable doing that. I see from your previous post that your friend is an adult. I assume she knows how you feel about her problem with alcohol and that you want her to get help. If that's the case, there is no need for you to do anymore. When she is ready to get help, she will. As long as people continue to 'help' her, she will continue as she is.
You need to accept that you are not going to be able to do very much to help your friend at this point. It is up to her to make the decision to stop drinking and get well.