I guess it's not normal for her to act the way she does.
Why don't you talk to her about it?
Maybe you should put an end to this relationship now.

From what you're saying, she seems to already "fade away" but maybe she wasn't feeling OK at that moment. I really cannot tell.
Just have a nice talk with her and figure things out.
Though, whatever you do, don't count on her "waiting" for you!!