Because Marisa wants to return the favor.This strip was posted on White Day, so presumably Alice gave Marisa a chocolate Valentine's Day.

Marisa, how did you get hurt?!

Hurt herself while cooking.

Ta-daa.

Come on, come on.

I worked hard at making cookies, so I want to feed them to you!

Eh, feed... I'll pass. I'm not a kid, I'll eat by myself...

Eh?

Wait, Mari...

How is it? How is it? Does it taste good? I tried my best!

What was that just now...?

*sway*

*nod*