Parvati didn't really know Sirius Black, but she knew who he was - everybody did! She'd always thought he was quite fit, really, though she'd never made a move on him; one night stands weren't usually her thing. Of course, the last time she'd had one, it had been with Sirius's godson, now her boyfriend.
Clearly Sirius didn't recognise her. She had no idea if Harry had told him they were dating, but she was curious about it. Beaming at him, she said, "Very adventurous, I'd love for you to surprise me. I'm Parvati." She had to wonder if the name would ring any bells.