The first time she and Danny have sex is a fumble of Ow, what are you-—Sorry, sorry, did I break skin?—You don't have to hold on so tight, I'm not going anywhere—and the crowning lie, It was an accident.
It never does accidentally happen again; she trims her nails, keeps her teeth to herself, won't hit or slap even playfully, and it isn't bad, but-
Her hand cracks across the Doctor's face. "I said, hold still," she orders, but he's trembling beyond his control now, an excuse to hit him again. She straddles his hips, grinds down against him, and drags her nails unrelentingly down his chest until it blooms pink and beaded red, until she can bring her fingers to her lips to taste him, until he's groaning from the pain and she needs to do it again and again and again…