Does she like being chased or just not interested?

So at my office I have been hanging out with this cute girl that works a few cubes away. We make fun of eachother a lot in a fun way and things are definetly very flirty. I dont know her all that well but i messaged her a few times on facebooks and she always responds quickly but thats it. She never initiates the messaging and never messages me back more than once, so i'll reply to her reply and that will be the end of the message. Whats going on here? I would make a move but she is out of town for 2 weeks so that option isnt available right this second.