Thanks for the question.
We all evolve in our own ways and something is causing a change in your girlfriend.
I'd like to ask a number of questions though, to gather some background information.
* How long have you guys been going out?
* Are you both in the same college?
* Has your girlfriend got any new friends in the time you've been going out?
* Has she joined any new groups or clubs in this time?
* Same for her family, have they started anything new in this time?
* Are you currently living together?