In the middle of a tough situation

You see, I have a friend named *amy and she has been on and off with her boyfriend. When I first met her boyfriend, he was nice and respectful. But then he left amy for another girl. A week later, he came running back to amy to give him another chance and she accepted. After that point, her boyfriend became a totally different person, being rude and obnoxious to her friends, including me. It was so bizarre because I had no idea why he suddenly changed. So, amy stayed with him for a couple more months and he left her, once again for another girl. She said she would never go out with him again, but after only a month or so, he came calling.

Amy came out of the blue one day telling me that she was going out with him again. I was shocked, but not too shocked because someday, I knew something was going to happen. well, my two friends are really annoyed at amy because of this. They are refusing to talk to her and my other friend believes that amy's getting herself into another heart break. I mean, as long as amy is happy, I'm fine with the fact, but my two friends will not let this go, and don't want to talk to her. I'm in the middle of all of this because all of them are my friends and two of them are turning against one. I know I can't do much about this, but how can I deal with this?

tell her to let go of this guy A.S.A.P. tell her that she is being weak and unfair to herself for doing this. GUYS ONLY COME BACK TO GIRLS BECAUSE THEY KNOW THAT THAT GIRL WILL BE THERE. so its like a habbit that guys develope when you LET them. the abuse wont stop. so there for, she should go off, find another guy, and let him realize shes FOR REAL. and once he sees THAT? his pride will be slightly hurt. but tell her its either him? or you guys. because no one wants to hang around some one so weak. (<<speaking from experence)