With what you have written, it clearly shows that she is keeping off you.
You have tried your best to know what the prob is, but she won't give in.
My Advice, to you is this:
"As a guy and to prove you are a real man, don't ever call her to end the friendship."
"Stay off her, don't call her for any reason, but don't be harsh and don't let it to be known to all that you two are distant."
If she sees you don't care about her, she would surely come to you to know why.