@icekatze
I seem to remember that Iori use to hit Minami quite a bit. However, I think that maybe most of it was edited out in a revised version. Iirc, it actually was kind of disturbing the amount of times she did it, and why she did it makes it even worse. This time, at least someone acknowledges it. But I get the feeling this is just how the author wants this story to go.
I know there is the tsundere trope of always beating the shit out of their love interest (which also needs to fuck off already since it is not a good cliche to use), and you often see that when someone messes up, the offended party (almost always the female) slaps the other. I think this time, it is playing with that cliche. Not that it makes it any more ok, but I can see where it may be slightly different, more artistically used.
Still though, I want to believe the author is just playing around that tsundere cliche, but using lesbians instead of the typical straight pairing. And that Minami is filling in for the dense MC. But given her background, it just doesn't sit well.
You are rught though, in the current version, she has now hit her 3 times, the first 2 were basically identical situations where Minami embarrassed Iori in public by kissing her, so she hit her on the head (like the cliche kind of hit, where minami becomes a chibi-like figure and such). This is the "first" time she slapped her. But like I mentioned, I think there was a previous version where Iori slapped her way more often.