i would NOT ask her to prom.
i mean.. she broke up with you. why would she choose you to go to prom with? you arent being realistic XD
its best to try to move on, im afraid. it will hurt for a while, but eventually you'll think about it less and less. for me it only takes about 2 weeks to move on from being disappointed. you'll get better at it the more it happens. sucks every time, but oh well. at least when you do find someone you'll want to be with them and they'll want to be with you, as opposed to only you wanting to be in the relationship, and them not caring about you or your relationship that much.