The difficulty can came come from a combinations or things.
a) Fear of rejection.
b) Knowing that if I'm rejected, I would have to deal with me handling my emotions (continually) while possibly being friend zoned. It can be easier just to never admit to them.
c) Not wanting to loose her as a friend, because I may feel she may doubt my intentions from that point forward.
d) over-thinking reason d
e) over-thnking reason e