Well, I know the reason he is going to follow her at first. Jamie needs to figure out whether or not he should hate her. He's a surprisingly honest guy, despite the fact that he works with some very ruthless people, and he won't be content until he's got himself figured out. By that point, it won't be hard to come up with a reason for him to stick around.

I'm thinking it is related to the fact that she shot him. Perhaps something with blood? She probably did get thoroughly soaked in his blood.

I also find it really funny that Laurel is more afriad of Jenna than Derek. Ultimately, Derek is going to be the one who causes far more problems for her and her cases than Jenna. Jenna's just a paralegal, and she really can't do anything. :)