Regrets.
Rebecca doesn't nurse regrets. She's made mistakes, certainly, large and small, but the way she relates to them is—
When something happens which shouldn't have, or if things went well but there were ways in hindsight it could have not, they run a fault analysis. If the analysis generates action items or growth areas, she executes on them or tracks that the relevant responsible people execute on them. If there are specific people who were wronged, and it's cheap and strategically viable or advantageous to make reparations, she has them made. If there was nothing she could have done, if they took a calculated risk and the dice just fell the wrong way, she closes the case and puts it in the archives.
The mental action of—sorrow, wishing she'd done something else, feeling bad about it—is not one she's configured herself to take.
But she understands regret, as a way people can be. She's talked many a young hero through their regrets in her Protectorate office. Failure is the only constant of the superhero life, and people have better and worse ways of dealing with it. Part of her work, in both capacities, is helping them cope.
When you don't understand all the details, the best thing to do is just be there.
She lowers herself to the ground and finds a rock to sit on, hunching slightly in deference and softening her body language. She doesn't offer any words of her own, but she attempts to project in her emotions—compassion, acknowledgment, affirmation, not quite intimate but not quite impersonal, more with the distance of a gentle look across the hallway.