It takes her brain a few crucial seconds to process the situation, really think about it, and come to the conclusion that yes, this is happening. He's actually doing this. Not only that, but North planned this, well in advance considering what he's already done as preparation. Preparation being, finding her size (somehow?), getting a dress, and concocting an inane story as to why she should wear it. She knew he'd been put out when she'd refused that day, but the specialist didn't realize his resulting tantrum would take the form of... this.
"Be that as it may," Ananke says, careful not to grit her teeth, or clench the slinky, slippery thing he called a dress too tightly her in hands, "even if you're recognized as a customer there doesn't mean that I would be. If the Jabberwockies are actually using the place as a front, it'd be more effective for me to infiltrate their employees instead." It's a very reasonable proposal. In fact, it's by far an improvement upon... this.
She takes a moment to hold out the garment and look at it. Really look at it. "Besides, this seems like wholly inappropriate attire for... anywhere." Not that she knows what people wear to clubs, but this can't possibly be it, can it?