Out of curiosity, what route are you playing with Brittani?
I also find the mother's introduction interesting. From a dramatic point of view, her mother in "Dark Path" is an element that adds another layer of misery to Brittani. Not only is she a girl who was supposed to have everything, and she has lost it with her parents' divorce. Plus there's a disgusting guy who takes advantage of her misery to harass her, and her mother wants to pimp her. It seems to me that she is going to share a place with Ashe as the most battered character in the game (in full dark path, I mean).
As for financial domination/blackmail, her mother is also interesting since she could be a "fuckable" character. I don't know what NeonGhost's plans are, but from the context it seems clear that Brittani's mother wouldn't mind pulling down her panties for a sugar daddy. The truth is that there are several possibilities here, but I don't know what plans NeonGhost has for Brittani's mother. But on that route she also seems like an interesting character.
And in the "boyscout" route, "simp" or whatever everyone wants to call it, although it interests me less personally, it could also be an interesting element for a perfect gentleman to help Brittani get away from that monster that is his mother. And now, for the simpiest simps, the dream is to redeem her mother and turn her into a good person. Again I don't know what Neonghost's plans are, but it could also be interesting.
In any case, the introduction of Brittani's mother seems to me to add a lot to the story. She is a detestable person, but she foresees a memorable character.