K bro, listen up and listen good... I'm about to drop some truth bombs:
a.) Find out where she works/hangs out/reads twilight books or w/e then stand outside the window furiously fapping while biting your lip and keeping eye contact. The eye contact's important - chicks dig that shit.
b.) You're on an MMO forum, not Rikki Lake-Online. If you're not trolling then I just suggest talking to her - talking's a good start because, you know, if you end up in a relationship with her that she doesn't know about then it's known as "Stalking" or "Being fucking weird" and is generally not socially acceptable.
Saying "Hi, we've not talked in a number of years, but your bust finally got big enough to attract my attention," is not.
Seriously, if this isn't a troll, the circumstances of you two breaking up actually matters. So bear that in mind. You two split before, so be respectful of her space, especially if she now has a boyfriend.
Try to be friends with her again. That can happen when people talk.
Just go talk to her. It's not a big deal if she says no, there'll be PLENTY of other women out there. But if she says yes, fantastic! So in other words, you've got nothing to lose and everything to gain.
Trust me, I've been there, in the 'too socially awkward to actually say anything' stage. I regret it immensely. Don't be like me. Just go to her and talk to her. Ask her out.