From what I've read here, your girlfriend is surely great, but also tends towards manipulating you. Also, most of the women I know always have a 'good' reason for avoiding the truth. What you need to do is learn to trust your guts. I've learned this after breaking up with my one-in-a-million. My guts never talk when everything's O.K. I didn't hear them (or didn' want to) and the **** happened. Later, I started listening and trying to do what felt right and all was well. I did stray from my instinct a few times and got hurt again (those damned moments when you see she really needs you, but only for a while). I started experimenting with this and my guts saved me from ****storms many a time since.
If it was me instead of you, she'd have to work real hard to make anything happen. Since that is not the case and I don't have all the relevant data, learn to trust your guts and thus trust yourself. If you feel the guts while falling in love, you must be able to feel what I'm talking about.
Although I understand the state you're in, I'd advise you against being such a wussie. The best of luck.