In her video about her life she talks about abandonment issues and family abuse as a small child. I think she is constantly seeking for the approval, acceptance and love she feels she did not receive as a child, but self-sabotages each time for fear of any more rejection.
I think she latches on so hard to the next man because she thinks he will be her saviour, the one who makes everything all right. When the relationship does not live up to the expectations she dissolves into the trashy, angry, bitter woman we all know too well.
I feel really bad for Logan right now. Raven is probably having a massive spac attack over the posts about Josh cheating and since she has no friends to vent to Logan will have to bear the brunt of it. We all know how well he deals with that, and how much he hates drama. Especially drama she seems to always perpetuate.