You can make someone a tomboy or girly, but you cannot make then "sexy and mysterious." The reader gets to decide that. Now, if you're talking about another emotionally closed off protagonist that most other characters find attractive vs someone who is outgoing and maybe even annoying, well I think we're getting dangerously close to "Mary Sue" territory with the first. My vote is definitely for the girly girl.
A l A little before my time I'm afraid. I can definitely see how it could work, just personally I find those characters to be a little frustrating in certain situations. Heard good things about the show, though!