She has been his superior officer, and is no longer. In the field, she had come to see him as a partner, not merely a subordinate.
She is a detective as well as a woman, earning her medals and commendations through skill and diligence. No unearned merits in her jacket. Looking at him now, she can guess what impossible thing he wanted. Isn't it the same thing she wanted? Barred to them both by rank and regulations in a world now barred to both of them.