Confront her in a quiet location of the store.

You quietly let her continue around the store, teasing shoppers here and there. Eventually you get to a part of the store with no other shoppers. Her attention turns to you.

"Can I help you?" she turns and glares at me.

You swallow nervously, but show no fear to her. You need something to gain the upper hand. You have the video footage, but need something a little stronger.

"I know all about what you do." You say confidently. There is something really familiar about her, but you can't place it just yet.

"Oh really, and what is that?" She replies scornfully.

Suddenly it clicked. You knew who she was!

"You are Katie. I know you, you live in the town a couple hours drive from here. That's why nobody knows you in this store. You come all the way out here to tease the unsuspecting shoppers."

You feel a sense of victory as the color drains from her face.