Should I be worried my boyfriend's ex-girlfriend will be at the wedding we are going to next week?

I checked out her myspace and she says she's going since we have some of the same friends. We HATE each other and I know my boyfriend still has feelings for her. Plus she's going alone.

How should I act? Should I try to keep him away or should I test him and see what he does when he talks to her? I'm a little worried!