You and Cassian grew very close leading up to the war, you became good friends. But now the war is over you seem quite withdrawn. You don't want to hang out anymore, you're always claiming "I'm busy". Cassian is worried that you're isolating yourself and fighting your trauma on your own.

He sees you now, putting your cloak on and walking towards the front door. He gets up from his seat and leaves the conversation with Azriel and Amren. He wonders into the entry hall before you hear his deep voice behind you, "where are you going?"

The truth is you haven't been avoiding Cassian, at least not deliberately. You are actually busy, busy learning. You have no control of your newfound powers and that almost got you and Cassian killed in the war, and so now you've been reading various books and going out in the woods to practice control of your magic. You need it to respond when you call for it, rather than just responding to high emotions. Right now you're preparing to go out to learn some more. You haven't told anyone about your research, you don't want to put the responsibility of teaching you how to control your magic on anyone. You'd rather be independent, atleast until you know some basics and you're not completely useless.