Should he still be talking to the girl he was involved with before me?

My boyfriend is currently not talking to a girl he had a 'friends with benifits' relationship with for around 6 months. I hate the girl, she got involved with him knowing I liked him and hid it from me for ages. I found out and flipped out at both of them (He is my best friend). Now, almost a year later, he and I are together and she is desperate to still be talking to him. I told him he couldnt, she has done horrible things to me in the past and I consider it a breach of trust and loyalty for him to be in contact with her still...especially since he slept with her behind my back. I told him I can't trust him if he still is in contact with her. I know he hasn't been for about 2 months or so, (they were previously still in contact but not sleeping with eachother before that) but she is moving interstate and having a farewell party soon. He wants to go to make peace before she goes, but I am furious that he is even thinking about going. He says he will be there for 10 minutes. I don't know what to do, I don't want to be too controlling but I hate that he is going to talk to her. I think she will start calling him non stop every day again. He says he is going for 5 -10 minutes to say goodbye to her and then he will take me out. Should I be upset? I want her out of our lives.