Gabriel rocks his hips, giving her very brief reprieves before driving himself fully in again. She's a demon, she can take it.

"Do your job. Make me come," he instructs her. Then he sends her an image of him covering her face, come dripping down onto her breasts to be absorbed by the ropes. Just to see how she reacts to it and help him decide if he should do that. It's just another way of marking her as his, after all.