I'm not saying she didn't learn how to flirt, I'm just saying it came later in (what we now call) adolescence, as opposed to girls of her age and social standing whose lives revolved around the dance of suitors and, er, dances :)

I think the reason she presumably never brought up the pirate thing with Will is implied in CoBP - "I was afraid you were a pirate...that would have been awful." Elizabeth may have her romantic ideals about pirates, but she knows what happens to them under the law. She likely wouldn't want to prompt Will into revealing anything incriminating. Although I also fully believe that she would've dropped hints which Will didn't pick up as a child.