Callie definitely has some skeletons in her closet - and I am guessing that it is those skeletons that are making her keep Jon at bay. They must be large skeletons - as it certainly would take a lot to constantly turn down Jonathan.
But I do think taking things slow is a good idea - it is too easy to "crash and burn" the other way.
And Kaner and Kennedy....hmmmm....an interesting dynamic there as well.