[For what it's worth, she isn't the only one in this room feeling uncharacteristically panicked and overwhelmed. Chekov is good at handling situations and emotions. There are brief breaks, but nothing that lasts and nothing that he can't deal with given time and space. He has lost people and he has coped. There's no reason for this to be different.
It is, though. Most relationships come easy to him. Everything with Kitty is a little more volatile, and it's different, but it's not bad. Not usually.
Then she's on the floor with him and his arms go around her automatically since that's where they wanted to be anyway. He doesn't know what's wrong with her, either. Is she really not mad?]