You have not demonstrated you're an alpha male. You were too nice to her, and too desperate. You weren't challenging her, and since she probably has low self-esteem, she needed to make herself feel worthwhile to someone who obviously didn't give a shit about her. That means she's found someone else.

The same thing that has happened to you, happened to me. She's just keeping you around in case the new guy(s) she's hooked up with don't work out. You're being kept in her proverbial closet so she can dust you off when she's bored.

Learn from this and move on, friend. I know it hurts. I lost the most beautiful girl I'll ever have in my life... she was fit, blonde with huge tits, 18 years old, and I'm a fat ugly balding 21 year old college dropout.

If you just can't get her out of your system, here's what you do. Eventually the faggot she's seeing now will cheat on her and she'll be all BAWWWW about it, and she'll be available one day. You have to be so cool and suave and demonstrate that you could care less about seeing her that she'll feel she has a new superior to demonstrate her worth to. It's tricky, but it can be done... there's more luck than anything to it, probably. In any case, don't hold your breath.

My final advice is to just do your best to put her past you and move on. Not what you wanna hear, I know, and for the record, I'm not able to do it either - I'm heart-broken. But do the best you can man... she's not going to lose any sleep over it, so you shouldn't either.