[She raises a hand in a solemn promise.]

I won't tell.

[And then she laughs, as she's told more about Ignis and what he's like.]

Kinda sounds like Yuuri-senpai -- except we have Yuki-senpai to keep us smiling, so I can't imagine her getting wrinkles every. She does a lot of the cooking, and keeping track of things the club needs. She's very responsible.