Something tells me it's Amatsukaze just reading the doujin out loud.
I think the punchline would be that, after Shimakaze finally mellowed and was willing to give Amatsukaze the benefit of the doubt, it turns out that nope! It really was that bad...
Honestly, I think the easiest solution would be to bang on the wall when she's doing it. Even if she only thinks someone is on to her it would probably set her straight. Maybe.
Hey, Shimakaze...Is that really what's happening?Hah!?Haven't you been listening to me?!W-What are you talking about!?But y'know...Amatsukaze, yeah?She's so serious and handy and stuff...But...I can't believe it myself either!I-It's the truth!So it's not like she'd go around doing something so dirty, right...?It's how it is!