my girl insists on being friends with the guy she left me for last time we dated.

My girlfriend and I met at college and hit it off. After some competition between a few guys we ended up together. we were seeing eachother last year and we had the overall agreement of monogomy. She had a friend which was one of very few people from home that she stayed in touch with. She told me she used to have feelings for him and they used to date and that he messed up her last serious relationship but there were no feelings there anymore. During winter break from school she made out with the guy from at a party and called me crying to apologize later that night. She said she still wanted to see me and couldnt wait to get back to school. When we got back to school she said she didnt want to see me anymore she was seeing him and stopped hanging out with me. After a while I tried to just be friends with her and it was obvious that we both wanted more. When things got rocky with the other guy we started fooling around again. However, when he found out through a friend he told her and she again told me she wanted to stop seeing me and see him. So I told her i was done and I wanted nothing to do with her. A few days later she begged for me back saying that he was a jerk and things didnt work out and she realized she wanted me instead. Reluctantly (and after some time) I took her back. We took a small break at the start of summer break and started our actual committed relationship shortly after. She then disclosed to me that she slept with him. We have been dating for about 10 months now and she insists on still being friends with this guy. She has lied to me about hanging out with him and has defended him in arguments. I know they still flirt from overhearing conversations and looking over an i/m conversation they had. She insists that I am being irrational when I tell her I dont trust her with him and that I dont want her to see him. I told her that I will not tell her what to do but that given the past problems he has caused she should know that she hurts me everytime she sees him. I am trying to be understanding and not get jealous and I have been allowing her to see him and not complaining about it. Am I doing the right thing or should she be willing to drop him completely if I ask her to.

She had a serious relationship with him before.
Warning.

MADE OUT with him during winter break.
Strike 1.

She BROKE UP with you and then begged for you back within a few days.
Strike 2.

LIED about hanging out with him while FLIRTING with him after she had HURT you.
Strike 3.

She is highly likely to cheat on you again.

I have actually been in this situation and let me tell you it sucks. If she cares for you enough then she won't hang out with him. She is allowed to call from time to time, but seeing him is a no no. You will never fully trust her, and honestly, she hasn't given you any reason to trust her. Sometimes we are blinded by our feelings and we take our lovers back. I hate to be the bearer of bad news, but she won't change. When things get tough, she'll come running back to you. There are far more better woman out there who will treat you right. I hope that helps.

Mate leave that girl alone! I have a girl who loves me and it wouldnt cross her mind to even speak to her ex. Go wondering and find a girl who is worth suffering for!

this girl seems like trouble. She keeps going back and forth. What makes you think that this time is different? Just move on.

drop the girl completely and forget about her. you got to be better than that.

Dude your a true idiot and a wussy, why in the heck would you even contiplate a relationship with this slutty behavior.... Theres too many good women out there that are respectful that honor relationships, go out and meet new women and have fun! She is basicly telling you your a piece of shit and wants her cake and eat it too, while you hang out for the emotional beating and your sticking around for it??! Maybe your IQ is real low?