Peri was completely absorbed in fixing her shoe, which is as impractical as all the footwear she owns in real life. The party has done a good job at dressing her. But it does mean that she wasn't fully prepared to look up and see a stranger also bent into the unnatural position. The affect, to her, appears somewhat threatening.

Making an undignified squawking sound, she reels backwards in surprise and just barely fails to keep her balance, teetering backwards before falling onto her butt. "Hey!" she says, sounding deeply wronged. "Cut that out!"