Have her take it right off again

"I wish you'd take it off again!" You're quick to tell the clerk, already taking the leash and instructions to put them back in the box. Right now you just want to be out and away from here, before anything weird starts happening about this collar.

"That's no fun at all...!" She's starting to object, but looks a little surprised to find herself doing exactly what you say. You're about to snatch it out of her hands, but she takes a step back and holds it protectively to her chest. For a moment she looks like she's going to try it on once again, but then hesitates as she sees that there's other people watching. "Right... Just come back later again, and we'll talk about it then? I quit my work in just an hour."

"Uh, fine..." You grunt, seeing that you're not going to get the collar back right away without making quite a scene of it. The audience seems a little disappointed though as you turn and leave, but they've soon forgotten about it and started shopping again.