It is difficult to know what is happening with your girlfriend. From what you have described, there is no clear evidence of cheating. However, it cannot be ruled out. It may be that she is unsure of what she wants at this time. Her confusion might primarily stem from the fact that she seems to be in a transitional period in her life.
Miscommunication may be at the heart of your relationship problems. For example, she thinks that you have relegated her to the “back burner.” In other words, she does not feel as though she is an important part of your life. If that is not your intention, then something is amiss.
You need to have an honest conversation with her about the status of the relationship. It can give you a clearer understanding of how to proceed. Tell her that you are confused. Let her know that you were under the impression that you and she were dating but that she is now sending mixed messages.
Clear communication is an important aspect of every relationship. It is a good habit to develop early in the relationship. Without it there will likely be problems.
Do you want to be involved with someone who creates the rules of the relationship without considering you? She believes that she has the right to answer your texts and calls only when and if she wants to. She thinks that her behavior is fine. She wants her space.
Yet when you give her space and stop calling her, she complains about it. Most people want, expect and deserve a response to their messages — oral or written.
If you need additional guidance, you may want to consult a therapist. A few sessions with a therapist might help you to know how to handle this situation. The “find help” tab, at the top of the page, can help you locate a mental health professional in your community.