I feel like many of us have been in your shoes. I just graduated from college actually and I've had different kinds of roommates throughout the years. One thing that I started to realize was that your roommate isn't necessarily there to be your best friend. When it comes down to it, he/she is ultimately going to be just your roommate...someone else who lives with you. Sometimes you do find a roommate who is going to become close with you, but they aren't all going to become that way. If she doesn't want to interact with you like a close friend would, then you should accept it and accept her the way she is.

However, since you said that you guys have become close, maybe there is something bothering her that is making her feel drawn back to communication and she doesn't know how to react. If so, maybe try asking her how she is and if everything is okay with her? If she says yes, then don't keep pushing her, let her open up when shes ready if thats the case.

Hope this helps!