Madoka nods slightly, her cheeks still colouring, and then obediently turns to go look at her reflection. For a few moments she just stares in silence, but then she slowly speaks up:

"You're right, the dress is really pretty.."

Really, the dress is pretty simple considering the selection they have available here. But Madoka is pretty easily impressed.

(And of course she's giving the compliment to the dress and not to herself.)