What is OKC?
Anyway, chicks usually do this when they're seeing someone they're interested in more than you, and then something goes wrong with that "relationship". Then they start calling the "back ups" that they were sort of interested in, but not overly crazy about. I have seen this happen TONS to many guys. They would flirt with some girls and try to hook up with some girls, and either get somewhat involved with them or the girls might not even let them have any kind of physical intimacy.
The same girl might date some guy for a year or so, and then it all comes crashing down with whatever they had. Next thing you know, you are getting a phone call from her just to see "what's up" and what not, and if you wanna hang out sometimes. Most relatinoships started like this don't really work out, but they are good for a quick rebound score, as selfish as that sounds

. So, if I were you, I would go ahead and try to hit it, but I would advise against getting seriously involved with her. A lot of times she will eventually go back to her ex boyfriend, he may have cheated on her or dumped her, but she could still be crazy about him.
I see this happen pretty often, and I would not wait too long, this is something that you need to jump on right away, 'cause next week she might be back with that dude, or have another sucker under her wings. Respond back right away and get her to hang out or kick it. You will find out quickly this way if you have a chance or not. If she doesn't wanna see you, she makes it easy for you to just move on to the next one and not waste your time. If she does wanna see you, try to hit it as soon as you can. Chances are she is on some kind of a rebound and pretty vounerable and emotional, easier to crack. Screw her brains out but dont' get too serious with her, as the time she ignored you definitely proved that she had someone else she was more interested in.