Most of you are more immature than you're making the OP out to be. Just because you're some big shot 20 something, doesn't give you a right to belittle anyone.
I can understand where you're coming from OP, when you give so much in a friendship it can be quite devastating to be second best. I would suggest, that you'd look back at the situation and maybe consider the fact that you may have exaggerated a bit. While I wasn't there and hence I'm not aware of the delivery, it sounds more like she just wanted to play with another friend who may or may not have been begging her to play with him/her for hours/days/weeks for all we know.
Imagine you where this "friend", wouldn't you be disappointed/jealous as well if this girl didn't even play with you at least once just because another friend of hers plays with her constantly.
My advice: Make new friends online and try to get a couple of buddies who you can play with sometimes. Also say sorry ;). And finally don't worry about it, if you guys talk constantly, you're not second rate. Look at all the movies and older people, they may go years without meeting their "Best Friend" but they're still the first friend they'll think about when the subject comes up, 'cause friendship has a much deeper meaning (I still don't know what it is though :/)
If you do have a crush on her, well that's another topic for another thread :P.