Can Cass predict what your character is thinking/planning/doing? Yup.
If yes, what limitations do you have on this? None. If she can figure out what Arthas is going to do next she's probably one step ahead of me.
Is there anything you'd rather she not be able to predict? Nah.
Anything else? I suppose Cass could see from his posture and fighting style that he's military or former military, ambidextrous but trained to favor the right, and is used to heavy medieval melee weapons and heavy medieval plate armor.