Theres basically nothing you can really do. Try to distract yourself by dooing something, meet friends, do something with your family, do some hobbies, etc. Going out with friends or play videogames while listening to loud music usually cheers me up when I'm sad. Don't just sit around and think, that's pretty painful at some points.
Also know that she's not worth it. Someone who does shit like that never deserves a loving boyfriend anyway. Sure, it hurts but since she's such an idiot you're better without her to be honest.