i can recieve her text messages, she doesnt recieve mine?? why?

I couldn't receive texts from AT&T customers because something went wrong with the number porting process when I switched from AT&T to verizon. Odd thing was, it worked fine at first, but eventually I could no longer receive texts from AT&T. I was on the phone with Verizon for at least an hour while they tried all kinds of things. Finally they generated a trouble ticket. About four days later I got a text message from Verizon saying they fixed the issue. Indeed they did - it works fine now.
Handcent has a setting you may want to try don't know if it works or not. Under Retrieve message setting you can request delivery reports for your SMS and MMS messages.

There is also a setting to auto convert to MMS, experiment with that checked and unchecked.

In settings do you have the "Compatability check" checked off?

One more obvious thing, does the number you are using for your GF include the area code?