I have never seen a better movie catfight than this one on terms of authenticity and emotion.
One thing that you may not notice is how the director leaves it to the women actresses to improvise the fight. There are no stunt doubles and only the most basic of choreography. The rest is left to the two women and when they slip and fall in the fight it is pretty clear that they are not planning on that.
In the entire fight, almost 4 minutes long there are only 2 edits. One when they cut away to the 3rd girl and the other when they go through to the second room. The entire rest of the time the camera is held static and the women fight in front of it, and when the sink or couch gets in the way, too bad. Great realism!
By comparison, if you look at the big fight scene in AMAZONS (a pretty good catfight too!) there are around 35 edits in the same length of the scene. At least in that, there are not the usual god awful cutaways to people fake cheering that we see most of the time in catfights in movies.
It is rumored that there were a handful of Japanese directors that would just let the women go for it, kind of makes sense when you look at the realism. I watched a clip of one actress talking about her catfight in a serial drama on TV around 1980. My wife translated for me and said the director did tell the actress to, "go ahead and slap her for real." The two really got into it and the actress said that they were both indeed pissed off at each other.
Your wife knows this better than me from the first-hand experience just how rigid Japanese customs are in the culture. Actresses, since the dawn of cinema in Japan, are obligated to be deeply thankful to the directors, producers, assistant directors for the ability to work, regardless of what cost it came to their humility and dignity. That said, since the culture is rigid and very arbitrary, there's no official gray area between legit big-budget pictures, and those, which came from less respectable sources.
It needs to be understood, that Japan changed mostly economically, not socially. When The Beatles gave a concert in Tokyo, they were largely hated, because the student movement of '68 was seen by older generations as subversion into their way of life that tried to uproot their society as a whole, and they won. What most of us can see in live-action and animation about other, magical worlds, lizard monsters and the heroes fighting them in mechas, it's all wish fulfillment. Heck, the very reason they travel glamour models to Guam for photoshoots is so they can sell a dream that there's a pot of gold at the end of the rainbow... when in fact, there's none. To count as Japanese, looking like Japanese isn't enough, you have to act like one as well, that is why Naomi Osaka was a low hanging fruit for the internal misogyny driven female comedians in Japan, whose path to success is to bring down a "mixed one".
So, when it comes to the director's instructions, we should differentiate between Girl Boss Guerrilla (or even Scorpion), aka pinku movies and Yokiroh, which was mainstream. Pinku movies were produced and sold for adult theaters, and women in prison movies and girl gang movies sexualized the seedy underbelly of Japan. They never addressed, how a portion of the Japanese crime life comes from marginalized people, whose parents were collaborators/loyal subjects of Imperial Japan, and thus could never return, but the new Japan, deeply embarrassed by its past, like the 3 monkeys of I can't see, I can't hear, I can't talk, denies they even exist. Imagine it like you don't get a birth certificate, without which you can't be a citizen, can't go to a doctor to get a clean bill of health, without which you can't work and could be deported to a country, whose language you don't speak. Only the black economy would employ you.
Your wife is right, it's not unheard of in Japan, where the stardom status of old Hollywood never ended, to pay the lead actress way more, than the others, thereby creating a rift that fuels bitter competition. Of course, in real life, their war is way nastier, than a catfight, they use uwasa, bad rumors to destroy the other's reputation. Last December, the pop singer's near-rape was a product of a jealous cast member feeding her address to her rabid fans, and the victim was forced not only to stand by her agency that didn't protect her, but also to deeply apologize to her fans for putting them through such an ordeal. You know the completely normal "victim goes on apology tour". As if that's a bigger mess, than indifference is.
Anyhow... I could never read the actual novel, though both fights are adapted faithfully. I commend the fact, that they took the step and filmed a novel written by a woman. The geisha in question, through her refined upbringing, could hide the fact, that her deadbeat father sold her to Yokiroh as a baby when her mother decided to keep her. When she became the leading geisha, her father resurfaced, this time sunken even lower, as he's connected to a whorehouse. The man the whore is dancing with is a factory owner, and by becoming his mistress, their financial troubles could be over... except Yokiroh is in dire straits as well.
This alone put them on a collision course, but the straw that broke the camel's back is that the prostitute isn't just her father's lover, she agreed to marry him. Now, up until the end of the last century, hiring actors to be your parents wasn't yet a thing, so the geisha's reputation would be ruined, if it became public knowledge that her father is a whoremonger, married to a prostitute.
So, the story itself allowed for the actresses to be more violent, but within reason.
