What's w/ her?

Here is a friend, a girl, who after a few days of our summer vacation never sent me messages anymore nor replied to mine. We'll we used to keep in touch through our cellphones. And I don't know any reason for her not to continue w/ that.

Then after a few days more, she invited me and some of our friends at their house for the celebration of her sister's graduation. I asked her then if she has any hard feelings or if she is angry w/ me and she answered no but she was not answering when I asked why was she not replying.

Then after that, she still continued that way. I was trying to call her but she won't answer the phone. She was refusing my call. Then when we met again, I asked her if she just don't like me(for that was the only reason that I, one my friends, & my brother knows besides her being angry w/ me) & told me no.

What do you think is her reason for that?