I can not really help you. But I can say that I am in the same situation. Kind of. I do not get the "I do not understand", but I get like "Thank you for the lovely compliments.". She is absorbing everything I throw at her, and not giving anything back, kind of. I feel used, and every move of affection I get from her, I do not know if it is pity or love. Anyway, I also wonder "Am I just fooling myself?"
Females are truly complicated. And they say males are stupid for not understanding. I do not know what they expect of us
I am sure the girl you are pursueing is great, listen to your heart =)