Key was to get in there as they were breaking up. You could have been that "Sweet, nice guy that listens and really cares about her" unlike that jackass of a dude she was with.
You blew it.
That's my secret anyways. Trust me, it works. If you sense a chick is having a boyfriend issues, get in there. Half the time you don't even have to do anything. Listen to her rant, and she's think you're the greatest guy ever.
There may still be a chance for you, though. Seriously, be that comforting, sensitive douchebag that girls think they want. She's vulnerable.