I agree with Jenna. Hook (as he did in comforting her when she watched Snow burn) is her strength, is a safe haven for her vulnerabilities…and that does need to happen so that she is no longer afraid of it.
Emma, in all her solitary stoicism and (some would say stubborn) strength, needs challenged. She already knows to what ends Killian will go for her. She already has made a physical mini-commitment to him (no, Emma, it was not just a kiss and never has been JUST a kiss) He is not going anywhere and he has been patient. Whatever she is going to reveal about her past is not going to be about being afraid of being hurt again. Neal already put her through that crappy torment and she grew passed him rather easily.
I feel it might be (ala a parallel to Elsa since they are heading in those directions) that she is afraid she might hurt HIM, physically somehow with the magic that she has always had, but hidden even deeper behind those emotional walls.
She has lost quite a bit of her snark with him, all those faux- cutting remarks meant to keep him at arms distance. Which he read well and understood.
***Always in search of a good flock***