Part of her wishes she could really see River's face, to read whatever expression is there. Ultimately, she's thankful for the masks. She isn't sure she could actually handle the sadness that is betrayed just a little in the tone of River's voice.

"On Darillium or in general? Those are...sort of two different answers. Things had changed so much by the time we went to Darillium." It's a massive understatement to say that The Doctor is bad at relationships.

She wishes this conversation was happening someplace quiet, just the two of them.