She sent you what she probably regarded as clear signals of interest, and if you haven't reciprocated, she may have concluded that you aren't into her. The early ignoring could have just been shyness, not wanting to seem too forward, or trying not to scare you away, but now it's possible that her feelings are hurt or she's trying to move on.
Other explanations, too, but from the OP it really sounded like she liked you, so it would be strange for her to suddenly ignore you for no reason. Did you ever return the compliments, go out of your way to hang out or do nice things for her, find excuses to touch her hand, anything like that? Does she know you like her?
Also, everything decided wrote.