Yes, Terrence was fighting dirty: he knew full well what tugging on her lower lip like that did to her. But that was the point, he was here to distract her, overwhelm her until she forgot to be afraid. And he wasn't going to feel bad about it when she was fighting just as dirty in return, making him muffle a groan against her mouth in return.
He had less freedom with his hands than her, since he was holding her securely against him, but he made the best of it, using his teeth to make up for it: even managing to bend his head to bite down hard on the upper curve of her breast through her shirt. He had to lift his head after a moment to see where he was going, but turned all of her available skin raw and red as they headed out the door.
Partly because of her fear, and partly because her nails digging into his skin was making him more than a little bit impatient, he only gave her a moment to adjust to being out in the rain before he turned on the spot, Apparating them up onto the roof. He dropped his jacket, which he'd somehow managed to keep in his hands, and laid her down on it, shielding her from the storm with his body as he rested on his knees above her.
For a moment, he grinned down at her, victorious. "Don't kill me yet," he said, free hands now sliding beneath her shirt and removing it easily. His mouth traveled over her bare skin, biting and licking, breaking the skin in some places, being strangely gentle in others, tongue tracing the tattoo under her breast. All the while, his fingers were working quickly to undo the fastenings of her jeans.
Only when he'd gotten them undone did he move to let the rain fall on her upper body, tugging her jeans off. He didn't move to shield her again, either, but bit down hard enough to break the skin on her inner thigh, then buried his head between her legs, tongue moving over her sweet spot every time thunder boomed above them.