Am I wrong/right in this situation with my BFF?

My best friend and I have been BFFs for over five years, in most of this time we have both been in long-term relationships with guys. About two months ago my best friend was dumped by her long-term boyfriend. She is now talking to this guy who we both went to high school with. We graduated last year. This guy was absolutely mean to through out high school. I was bullied a lot mostly by girls, but this guy took the cake on being mean to me. Every day he would call me degrading names (use your imagination) and would constantly mock me. I never started anything with him, he is just a naturally mean person. One of his friends even aggressively pushed me into a locker. Basically this guy and his friends made high school hell for me. This guy worked in the yearbook committee and he even printed a mean thing about me in it. This guy and my best friend had a fling a long time ago but have recently re-connected since he is home from college. He has told her that he wants to date her over the summer but once he leaves for university he no longer wants commitment. Of course since she's on the re-bound she is falling for his company. I am angry with her because I can't believe my best friend wants to date someone who was so mean to me for no reason and made my high school experience like hell. I have told her that I don't want my feelings to get in the way of her being happy with him and that I can't be happy for the both of them. Am I wrong to have such feelings towards these two and how should I appropriately tell her what I think? Despite who the guy even is I don't want my BFF dating someone who just wants to get lucky over the summer and will break her heart again. I am in no way jealous, I am engaged to the man of my dreams. I just want to have a normal relationship with her again, but this shady dude is getting in the way. She is going to be my maid of honor and if it did work out between them there is no way I could let him come to my wedding.