honestly, asking her phone number and instead, she ask it back demonstrates that she has a higher value than you...you can either close game here, or just go back to her and say that...i thought about it for a while, and i still think that it's best for you to leave me your phone number...

if you know her background as in her study area and so on, lets say pharmacy...just say that i would like to make friends with a future drug dealer or if she is going for law, just say that if i needed any future lawyers, i know who i have in mind to probably pick it out...honestly, being cocky funny here is one thing, but...it does not guarantee success as well, just put it in mind as, well, if she doesn't give it, it's her loss...no big deal...and don't go there anymore until she left...just my thoughts...

if she really had interest with you, she will give you her phone number...nuff said...=)