If she's never been interested in me, then why is she going cold now?

umm.... why are you even asking this question if you've never made it clear how you feel? sorry for being harsh, but grab your damn balls and ask her out. thats the only way you will have an answer, then you can stop speculating and wondering why this, why that. everything will be clear, and worst case scenario, she says no, and you move on...next! and dont be scared of rejection, everybody gets rejected in their life