What helped, in that moment, more than he understood, was the fact Helen could get inside his brain. He was Oliver Wood, after all, and if there was thing Wood knew, it was Quidditch. Which meant he would equate everything to that scenario. And it would work to her advantage, more than he knew. Knowing one's enemy? Well, it was invaluable.
So she watched him then, his eyes focused on her shadow, and she realized what he was waiting for. She smirked, pulling back even farther as she finally said, "I'm not going to fall for that, Wood. If you want to take me down, you're going to have to come for me."