hmm here are a few confusing thoughts...
i think Liz is tired of men who are perfect and ALWAYS do the honorable thing. She wants Jack to be good but not too good...
I dont think she knows what she wants at all. She is just being piraty and trying to push the envelope and get away with whatever she can. I do think she wants Jack to be good at heart, (which he is) and she knows he is, but how good is good?
plus, like all women, she likes getting attention from guys. Jack is extremely charming and affectionate. Her self-esteem is probably all torn up being dressed all grunge and stuff, and not having Will constantly there making puppy-eyes at her, so she's wondering, even though I am "off the market" am i still desirable? can i still make men want me? etc. she gets a rush from it. then she stumbles into scary territory when she realizes her feelings for jack may be deeper than she thinks...