"Really?"

Eponine really wants to believe this girl that everything is free, or can be bartered for a song or a flower. But nothing is so easy and simple, surely. And then the girl calls Eponine beautiful, and Eponiine knows that she's lying. Understanding twists Eponine's lips to a self loathing grimace. The girl is making a mockery of her.
Montparnasse has before. He let her dress in the clothes of the women he killed. He let her think she could keep them, until he laughed at her and called her names and made her take them back off.
The girl's doing that too.

Eponine goes to shake her head, but she remembers the soft fabrics. She remembers how the corsets had pushed her breasts up and given her cleavage. She remembers how they had felt like a hug. Like she wasn't alone. And she remembers feeling pretty, for that split second before he'd laughed, she felt pretty.

So even though Eponine knows that Nancy is going to laugh at her and humiliate her, she nods.

"I'd like that, Miss."

After all, a short memory of something nice is better than nothing at all.