Is she actually interested or am I wasting my time?
You’re probably not gonna like my suggestions, but here goes: , you are wasting your time and she is manipulating you. She knows very well that you’ve developed a thing for her, and she is just amusing herself while fueling your interest in her and watch your reaction. It is a way of pleasuring oneself by giving subtle romantic/flirtatious hints to another person and watch the reaction, but not taking any decisive action like to accept an actual date, or to actually ask the person out… kind of like being mysterious and enjoying the perplexity in the other person’s responses. I don’t know what your mindset is, but regardless of being a guy or a girl, I absolutely hate this kind of behavior from the opposite sex. It is better to be bold than be mysterious. You have been bold in your actions when you asked her out, but she is playing the mystery card and you are being victimized. Well, here are some suggestions:
Try to avoid her as much as possible.
Stop making jokes when she is there.
If she calls, ask specifically does she have a study related question. If not, then say you’re busy and hang up.
Do not answer her messages on facebook, unless they are really important or work related.
Try to focus on things in your life other than those that involve her presence.
If she comes up to you, say ‘I’ve got this or that to do bla bla bla, see you later’ and go away.
Shape your daily life in such a manner that this girl becomes completely insignificant to you.
If she asks you why you’re not talking to her, simply tell her ‘I’ve got other things to do besides getting bored’.
Having done all these, if she is interested in you, she will come to you. And if she isn’t into you, she won’t care and mind her own business. Either way, you’ll get your answer. Till then don’t torture yourself wasting your brain with thoughts about her, she is not worth it.