usually parents, or at least one of them, are the persons who will love you the most in the world, so you should tell her that they will eventually get over it, whatever it is that she did they will eventually forgive her but that she should really stop drinking because it will not solve anything for her. She should try to make up for her mistakes not keep making further ones...and even if her parents don't get over it well life moves on and she has to appreciate the good she has like friends tht worry for her like yourself.