@altecz,
If you don't have the information for her mobile, it'll have to be facebook - it's better than stalking her on campus. That would be creepy.
It can be something as simple as letting her know when you'll be on campus and suggesting a get-together.
hey M, I'll be on campus Tuesday afternoon. want to catch up over a coffee? what's your schedule?
she might just say no. you let her know it's cool and suggest she let you know if she'd like to do that some other time.
No problem M. Let me know if you want to meet some other time. (then leave it alone for a while)
she might say not Tuesday. you ask her what day is good for her. then set up a day/time/meeting place.
she says yes. you confirm a time and meeting place.
all of those things are fine - and better than where you are now.