firstly, did you read the signs correctly? scally you "think too
much"?? 
secondly, maybe you took too long to take action, and the opportune
moment is lost. some guys just have bad timing.
thirdly, maybe she has some other problems that is taking all her
attention at that time, so no time to think about er2 nu3 si1
qing2?? i mean, you never know...
finally, maybe during the whole time of dropping hints, she
realised that you're not REALLY her type of guy?
can have a lot of reasons de lah...