What would a marionette do (слэш)

"Care to tell me, why miss Weasley keeps sending me dirty looks at breakfast?”
“Notice that did you?” he asks and without any input from Severus continues, “that’s of course because she thinks I’m cheating on her with you.”
“Are you?” A corner of Potter’s lips curls upwards.
“I think you would know if we were fucking, Snape.”