Only a insincere apology and that's it? Nothing was resolved and the mom showed absolutely no change whatsoever. Does this ever get addressed at all later in the novel?
maybe she'll just never factor into the story again, and Yuuri will be allowed to finally live in peace without her family rearing their heads anymore.
that's the best I can hope for, because there's just no way the mom's going to face any consequences. This isn't the sort of story where the "good guys" (MC and his harem) are going to go actually fistfight or attack people, so there's no way they'll do anything other than Talk At the antagonists and act like that resolves things. Plus, the point wasn't forcing actual karma upon the mother; it was having Yuuri be freed from the abuse of her family, along with a chance for the MC to finally explain the bigger part of his backstory and reason for doing what he does. As infuriating as characters like Yuuto and the mom are in manga stories, they're generally defeated by the main cast achieving character development.
Honestly I would just headcanon it, and pretend that as they're driving away, the Mom continues berating Yuuto until he snaps completely and stabs her from the backseat while she's driving them away. Then, later on when the MC's having dinner with Yuuri at like a diner or something, there's a television news broadcast in the background about rescue teams pulling the bodies of an adult woman and an adolescent boy from the river after finding a car submerged after it smashed through the guard rail on a bridge.
Sometimes you have to write your own addendums to stories.