I don't like the author's afterword explaining Momoka's argument. It looks poorly done, and it also looked like Izumi's response of Momoka's argument being valid was sloppily done.
We, the readers, know that Momoka does not know the entire situation.
Asahi and Izumi know that Momoka does not know the entire situation.
Tsubasa knows that Momoka does not know the entire situation.
Momoka herself knows that she does not know the entire situation.
In that context, where Momoka does not follow up with the author's stated retort line of "It's not like that, right?", the most straightforward interpretation is that it's not merely her using a rhetorical formula. She didn't complete the formula. It looks like she's being serious because she doesn't know the full situation.
And it's apparently not just a cultural difference where I am unfamiliar with the Japanese formulaic rhetoric. The author said there were a bunch of comments that the author read, presumably in Japanese.