It cuts both ways. He is into her, and she is....I don't know. It seems like that situation, unfortunately, is out of your hands. And it sucks, so being sad is inevitable (cry it out, etc) .
But then, like I think Dionysis kind of said I think, go out and do something about it. Run off all that negative energy you have (I would be mad too!), and do something to make yourself feel better. Find your best friend and go get a makeover. Run, run, run. Or buy something that makes you happy. Do something good like community service or find a cool, new organization to belong to. Being busy helps so much, and consequently, that is a great way to meet people.
As Tony Robbins as this sounds
, only you have the power to make changes in your life. Make the boy sorry that he is not choosing you. Trust me, that is the sweetest revenge, and you will get the most out of it. Don't let this get you down. I am rooting for you.