Can You Help Me Get Things Back To Normal?

Last summer this girl and I were like best friends even into October we were really close. Then we didn't hangout that much for like a month and in December I found out that she was dating this guy. This guy 1: I know for a fact hates me. 2: Had gone out of his way to humiliate her in the past and 3: Played constant head games with her. Of course I was upset when I heard about this but I figued it wouldn't last long, as of now shes still with this loser and hangs out with his friends all the time, all of which hate me and some of which she hates. Furthermore the relationship has only gotten worse: he smokes pot, puts her down, blows her off for another girl. I still hangout with her but its hard its usually only for like an hour or two and its always hard to set up. I just want things back the way they were last summer how do I get that? BTW sorry this took so long I just needed to explain the situation fully.