It was almost too easy to get the Master to do what she wanted, all she had to do was offer him sex and he'd agreed to anything. It was sort of win-win really. Particularly in this case since he was basically agreeing to being tied up which meant she could probably do anything she wanted with him.
When he puts his arms around her her she turned her head to look at him, removing her gloves quickly. "I could always stick you in a cage next to the demons," she offered, "kill two birds with one stone, as they say."