It sounds like you and I have the same friend. I usually just listen to what she has to say and offer some small comments. It really doesn't matter what I say because she is so intent on complaining she is not listening to me. She says just talking makes her feel better, so I listen.

I have to warn you though, this type of relationship gets very burdensome. I get tired of hearing her complain and gripe about everything. Sometimes I don't answer my phone because I need a break. I wish I never took on this role and that I coud end the relationship without hurting her. I get nothing out of our friendship.