I think the healthy thing for you at this point is to set your priorities for yourself... and I don't know that this girl can be "won back" now. I think if you feel like you already tried your best, and over the course of 6 months nothing happened, and she started something up with this other guy... you should just move on, in my opinion.
But hey, all is not lost. Get your financial situation fixed up, and make some plans for yourself. Take this time to set your path, give yourself some goals, that sort of thing.
I know it sucks to lose someone, and not be able to win them back, but it's just not always going to happen. Be happy that she's happy, and I'd also recommend to distance yourself from that whole situation. Because even IF he turns out to be a huge asshole, bad for her, etc., it still won't make you look good to have dug and pointed it out. It just won't.
So, pull yourself up and keep looking forward.
