Imma be a bit cautious with my wording here... I recall there being
some talk about a "partial harem" ending which, in essence involved a general acceptance of Jenna as part of the Katie, Debbie, Lilly group. I also recall some talk about others (depending on who MC allows to stay at the beach house) being "tolerated" by one another. Now, what I am sure of is that CG never gave a definitive answer but was
considering possibilities. So, the safe bet is to approach it as you say, "monogamy" is the rule, polygamy is the exception, in this story. All in all it's wait and see for the final chapter...
Jolina and Bella have some history as well as being in
cahoots for the inheritance. In the first iteration of the story I didn't believe half of what they said were their reasons for their behavior and ran them on down the road. Having gotten that far in the story makes it difficult for me to even give either of them the time of day in subsequent play throughs. 'Course, that's just me.
That decision might have seemed "out of nowhere" for you but, I doubt it was that way for the dev. They gotta make a living, man. Overall this rework will have encompassed less than 6 months since the release of chapter 24 if they keep to the announced schedule. That seems pretty efficient to me and it didn't really come as a surprise since they talked about the possibility quite a lot before making a final decision.
Only 157 huh? Your gonna make me think the average IQ around here has increased drastically.