When something's getting away from us, it's our instinct to always try harder bro, it's human nature...there's a great upside to that, but in affairs of the heart alot of times it makes things worse :-P
I just have the feeling the tighter you squeeze her, the more apt she's going to slip through the cracks on this one. How do you think she'd react if she found out you're monitoring her cell phone bill? She might walk out the door right? Just food for thought on the reality of the situation.
Cutting someone loose to see if they really want you and will come back no strings attached is a tough assignment for anyone, but alot of times it's best.