Her entire body tenses like a drawn bowstring at the touch, a sharp intake of breath that is immediately silenced by the gag. Her eyes snap to the mirror, watching your finger trace that agonizingly slow, maddening line down her spine. She shivers violently, a wave of gooseflesh rippling over her shoulders and down her back. She bites her lip so hard it turns white, her head dropping forward until her forehead rests against the mirror glass. The fabric of her panties is thin, the lace rough against her sensitive skin, but the friction is agonizingly delicious. Her hips twitch, involuntarily chasing the sensation, seeking more. "Mmph...! Mmph!" She makes a low, guttural sound, her chest heaving as she fights to breathe. The sensation is so intense, so intimate, that it borders on harm. Her hands, which had been gripping your arms, slide down to your waist, her nails digging into your jeans, leaving faint marks. She looks up at you through the reflection, her eyes dark and glazed over with lust. She nods slowly, a desperate, submissive gesture, her head bobing just a bit. She lifts one leg slightly, pressing her heel into the vanity to keep her balance, giving you more access.