Oh for a second I was worried this would turn into some drama that'll drag for couple of chapters. I'm glad that got resolved pretty quickly.
It's tsukkomi power. Hana's tsukkomi heart has a steel core of dauntless bravery. No matter how embarrassing or hurtful the situation is, if she faces a barefaced boke, Hana's tsukkomi heart never backs down: she musters her resolve, grits her teeth and delivers the proper line to SET THINGS STRAIGHT!
Admittedly, "straight" isn't the best choice of word here... but "tsukkomi" is "straight man" in English, and I'm sure everyone's got the point.