Considering how much you appear to hate this girl, I'm not sure we can rely on your perspective to be an accurate account of things. Your crush/ex-crush being intertwined makes things even murkier. All of us are prone to providing biased information, and all of us can't help but not include all the information, especially when we guess at others motives.
You say she's a bitch, but the only example you've given is excluding you. So she doesn't like you. Just because she likes most people in a group, doesn't mean she is obliged to like all of them, and absolutely does not mean she has to invite all members of a group to be friends with her on Facebook, or to her parties etc. By itself, this isn't bitchiness - every person has this right to choose who they want as friends.
Put another way - just not liking you is not
being bitchy - otherwise you could describe every person in the world as a bitch. Just not wanting to hang around you is not being bitchy - same reasoning.
To be bitchy, there has to be more to it than just not liking a person. There also has to be other things like: condescension, gossiping about ### behind their back, being two faced, sabotaging behaviours etc.
So perhaps you see the irony - that you will find most of these behaviours in your post?
Things don't have to be this way. You can't control other people. The only person you can control is yourself. Being true to principles you admire always reduces confusion, increases your sense of who you are, and builds self esteem...breaking principles you admire always increases confusion in ones life, decreases your sense of self, and reduces your self esteem. The path we take towards or away from confusions, towards or away from self esteem - is a path we choose.