It sounds like you've pretty much made up your mind already. You don't trust her, and since she's not coming clean until forced that leaves me thinking that there are two possibilities:
1. - She's really into keeping her own space and secrecy is how she does it (yeah, right....)
2. - She's not sure
what she wants and so is trying to have it all.
I'll be the first to admit that I'm a bit jaded when it comes to women - take my
Poll(also on the Tilted Sexuality page) and you'll understand after reading the comments. However, I think that you need to sit her down and explain that there are certain things in your relationship which trouble you and that from now on it has to be completely open and honest - or else it has to end.
If she agrees, then don't pressure her further on the matter. But if you find out she's lied to you - or if she's not telling you important details which you feel you need to know - then again: end it.
All you can give her is a chance. Ultimately, it's up to her to prove to you that she's changed her ways. Like a few folks have mentioned so far, she's come clean with you now. There's
got to be something there for her to do that.
Part of your being hurt comes from the fact that what you thought you knew about her was only part of the picture. That's always rough. In time, however, you can work past that....but only if she continues being truthful and worthy of your trust.
Good luck, and if you need any support or anything just PM me.