I'm starting to half suspect this is a deliberate deconstruction of Iori's character - she's more and more starting to resemble the old Shizuku, only without the latter's Freudian Excuse of legitimately horrible past, self-awareness and almost-desperate desire to reform.
I kind of thought of that, but that opens up the suggestion that Minami has some kind of supernatural power that makes people hit her. (I'm exaggerating, of course, but I don't see how you avoid some kind of victim-blaming in such a case.)
I mean. From what we've been told Minami should be quite physically capable of resisting such mistreatment if she wanted to, particularly in regards to Iori who as far as we know has exactly zero brawling experience. That she didn't and doesn't is thus presumably due to psychological/emotional factors, ie. a need for companionship sufficiently pathologically deep-seated she'd rather suffer abuse than risk the relationship.
Put harshly, she is to a degree enabling continued and in this case apparently escalating abuse from her SOs by outright refusing to stand up to them despite being fully capable of doing so.
This is in conspicuous and I suspect not at all unintentional contrast to the relationship between Shizuku and Saori, where the latter immediately made it clear she will respond to any misbehaviour ferociously and to the full (and considerable) extent of her abilities. Which if anything seemed to come as something of a relief to Shizuku who knows how seriously maladjusted she is and needs someone capable and willing to keep her in check while she's trying to work out this whole "decent human being" thing.
...I'm going to be so amused by the grim irony if this ends up with Iori just getting all the worse and eventually Shizuku of all people having to stage an intervention.