You're not over reacting. Your feelings are valid. You have explained yourself to your girlfriend and she is disrespecting you by cutting off communication. It's the long distance equivalent of the silent treatment, which is incredibly unhealthy. I think you should have a good chat with her and be honest that if it continues this way than you can't be in a relationship. You need something that is healthy for you.

Note I am a very cut to the chase kind of person, so keep that in mind with my advice.