My perspective: Nano isn't entirely blameless, but doesn't deserve the kind of dragging Sinder is getting. When it seems like one of her biggest clients is trying to push for her exclusive service at the expense of everyone else, she goes along with it because this is her income and the likely idea of "If I lose Sinder, I'll lose a lot of money", when the counteroffer being given is along the lines of "If you cancel someone else's art, we'll pick up a commission so you're not out money". Yes, she was still complicit in going along with it, but presuming that this is her only source of income, she was probably trying to find a way to minimize the damage done to her own finances without having to really lose anything, until it got to be too much drama bullshit and the idea came out to just drop the bombs.
I didn't read everything end to end though, maybe I missed particularly damning evidence against Nano. She just seems kind of spineless/self-interested to a point where it's just too much to continue to bother with.