Looks like she's about to kick some Just Monika ass.

Monika: “Oh? You’re approaching me? Instead of running away, you come right to me? Even though your best friend, Yuri, told you the secret of my powers, like an exam student scrambling to finish the problems on an exam until the last moments before the chime?”
Natsuki: “I can’t beat the shit out of you without getting closer.”