She swallows thickly at the mention of the place. Her voice is barely even a whisper. "Katarina and Sara..."

While the Doctor would mourn for all of his lost companions, whole planets being laid to waste was in some ways more painful.

She squeezes his arm. "You were left with no other option."

Which is a reoccurring theme in their long lives together. "Or more accurately, you were left with the option that would save the rest of the universe."