Korrupting Kayla 2 was a great inclusion. It's nice that Kayla is always a slower burn to get to the really raunchy stuff. I'm a little sad that her characteristic submissiveness seems to be going away, but it offered more growth for her character, so it makes sense.
Surprisingly, I was very interested in Marie's mini arc. I don't think we've gotten a story dedicated to a mother being warped into a family slut. So it felt somewhat novel, but also felt like a twisted form of justice given her behavior throughout. Really hope to see a little bit of where her story goes and her continued debasement at the hands of DomCo.
Thanks for the comment! Marie will continue to have a role and her own transformation ARC, which will be used to show more of Kayla's growing cruelty toward other women. It was a hard thing to start pulling Kayla out of her submissive nature, as that was a big part of what made her fun to write in the first book. While she still retains some aspects of that, she did have to start taking on a more dominant and grown-up role to get to where she will eventually need to be at the conclusion of the series.
In some ways, Kayla is the ultimate change arc. Shy, innocent, submissive, and kind at the beginning. She's sweet and likeable. However, after being taken advantage of by almost everyone around her, and constantly pushed to be sluttier, meaner, and to view herself and other women as inferior, she loses a lot of those qualities and becomes villainous.