OK, Childish revenge #1 - on your profile page you can put "Aimsmum is...wondering why people put profile pics of themself with other people's boyfrinds..."
Childish Revenge #2 - put loads of BAD pics of her on your page with the tag "just a lovely pic of friends on a night out"
What I would Do: Put a pic of you and dp, with him looking adoringly at you - make sure he uses the same pic as his profile pic..the fact that you have the same one will be so cutesy...make sure you both change the picture alot so she will be bombarded with one picture after another of you and dp looking nauseatingly happy together...
The High Road: Ignore ignore ignore. You have him, he loves you...she will probably move on if there is no drama attached to it all.
Good Luck!!