Well, it was Valentine's Day. They were romantic handcuffs.

"Fucking perfect," Annie mumbled, planting her foot on the bed so she could rock her hips up to match his movements as best she could. "I love how you feel, Diego, you're so good --"

Annie was kind of just stream-of-consciousness sharing everything in her head at the moment. By-product of being super riled up and denied her primary means of showing affection, probably.