Pisces guy and cancer girl?

i recently met a cancer girl and she is awesome. we talked online for a few weeks and then we just met the other day for the first time. it went good and i couldnt keep my hands off her. we almost ended up having sex but she didnt want to do it the first time. you could tell she really did though. well i think the problem might be is that im going to be leaving soon out of state and she knows this. to be honest ive never had a girl resist me when things get frisky before so its kind of frustrating lol. is she afraid that i just want to have sex and leave town n nver talk to her again or is it something else? i really like this girl and she just really gets me so i would never play her that way. what is this cancer girl doing? is she protecting her heart?