I've posted this a few comments back, chapter 48 of the manga corresponds to chapters 102 to 105 off the novel. The divorce seen we see in the first chapter of the manga starts in chapter 164 of the novel.
Considering that each chapter of the manga covers at least two chapters of the novel, never less than that, the divorce should happen in 30 chapters at most.
Considering the events due to happen yet, my bet is between 15 and 20 chapters.
Does anyone know when they get divorced and Navier leaves this asshole? I WANT LEAVE THIS PLACE UHG