How do I make my ex jealous at a party?

I thought I would never see my physically abusive ex ever again in my life, but apparently I am. My "best friend" invited me to her party this weekend and invited HIM too. She knows how much he hurt me but lately has become friends with him. I really don't want to go, but she's saying i'm a bad friend if I don't. Anyway it's a pool party and i'm going to be in a bathing suit. How can I make him jealous? I don't want him back, but I want to show him what he's missing. The most he's ever saw me was in shorts and a tank top, so a bathing suit will be interesting xD