There's no reason to say anything about it. Everything has gone back to being (relatively) normal, and besides, Mari knows that Moe was never angry at her, and is probably incapable of ever becoming angry at her. Still, the thought crosses Mari's mind with a steadily increasing and slightly alarming frequency: was King Torture correct? Would Mari really have allowed Moe to sacrifice herself in exchange for her own freedom?
Superheroes absolutely must have a strong sense of self-preservation, she reasons, or else how would they ever survive? But this seems like a flimsy excuse, even to herself, in the face of Moe's unrelenting selflessness. Mari knows that perhaps she can sometimes be a little difficult to work with, but Moe has never once let her down or abandoned her, whether they were recording a song or defending against evil. So yes, she thinks, maybe an apology is in order.
"Mari-san, I don't understand," Moe says, after Mari has worked up the nerve to actually say something resembling an apology. "What do you have to be sorry for? We're both just fine. And it all worked out, didn't it?"
Well, Mari thinks. Yes, it did. But… "You're so brave, Moe," she says eventually, because what else can she say.
Moe brightens instantly. "So are you," she replies.
It was the right thing to do, Mari thinks the next day, during a break in recording a new song. And when Moe peeks over her shoulder to look at the schedule on the table in front of her, Mari wastes no time in leaning up to give her a quick kiss.
There might be a little more meaning behind this one.