Yes red herring is the correct term.

Lily the mastermind behind it all. That would be the ultimate twist. I would have a new found respect for the father is his side piece was Lily. Or maybe not because she would had to have been super young when that started. Can't see any of the young women being involved in the will. No Jenna, Debbie, Lily, or Katie wouldn't make sense, but just about anyone else could be possible.
Obvious culprits would be Elaine, Bella, and Jolina. Zarah, Monica, or Theresa less likely but still possible. Angel maybe Wanda less likely but just my opinion. To me Theresa has always been a red herring who could put up with her shit for that long. Zarah doesn't seem like someone his father would carry on a long affair with plus seems like a trade down from Elaine.
Monica would be the surprise and could solve the whole incest patch thing too.

Do we ever hear about who Katie and Jenna's father is I don't remember.
Well, I am not saying Lily is the mastermind... but, maybe, Monica is the other beneficiary of the will, and only get her money if you don't get yours. That would mean you stay with the girls for Love... while they seduced you for money...
Mom (Monica) got the kids in on it, Jenna hacked your account so knows you can't stay with them, and if you do you lose your money. Katie and her friends help with the seduction. After the reading of the will when you say goodbye to the money to be with them, they say goodbye to you and get all the money.
Seems very (yes, very) far fetched, but not entirely unplausable. I have seen worst in real life, so a game could pull this off without bending phisics like Sponge Bob Square Pants does.
We already knew there are 2 gold diggers, and that (in the dads words) Elaine is one of them.
. And for it to be a very secondary character like, Zarah, Angel, Theresa or Wanda would not make much sense (In my opinion anyway). Only leaving Bella or Jolina to be pretty obvious choices. Even though Jolina is kind of falling of the rader as others have pointed out. And even Bella is kind of secondary.
So the Gold Digger must be, to my horror, Jolina (noooooooo), or Monica (with help from Katie, Jenna, Debbie and/or Lily (blasphemy)).
Whats more, we only thought it was not Monica, because Jolina didn't ID her from the photo we showed her, but now knowing who Jolina saw... It could be anyone.
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Damn, I am rambling on. Anyway, great update. Now I will put my joy on hold until the next release.
Have fun and keep safe.