In the Simon/Kaylee follies, unlike most people, I generally side with Simon. Kaylee has a script running in her head about how things are supposed to go, and not only is Simon not on the same page, he's in totally different play most of the time. So instead of just telling him what she wants, she gets mad, flounces off, and he has NO Clue what just happened. Even though it's clear that they like each other, I just really find that Kaylee is unfair to Simon a lot of the time.
I think she is childish and avoids adult discussion because she really
likes him and all of a sudden for her there is a lot more at stake than a roll in her bunk. She can flirt and she can flounce and the ball is still in the air, unfair though it may be to him as he is cast as the idiot in this game. But.. the game is still afoot. If she is an absolute adult he might say "no" and then it is all over.