I have a reunion to attend next month, and my ex-best friend will be there. What's the best way to approach this?

Next month, a friend of mine from high school and I are hosting a drama club reunion for all of our old high school friends. I’m extremely excited because the majority of these people I have not seen in at least 3 years. However, my ex-best friend will also be attending. It’s a long story, but basically she betrayed my trust by using all those little secrets I confided in her as ammunition against me. She also chose her now husband over all her friendships and lets him control her daily life (and I can’t respect people who become doormats for their significant others). Normally I would deal with this situation by simply ignoring her existence as to not cause any drama (at the drama club reunion, ha). However, I feel that is not the correct way to approach this. I know I can never forgive her, and even if I did things would never be the same between us, but I do wish to be civil with her at this event. I just don’t know if I can control my contempt. What would your advice be?