As for the possibility of betrayal in every relationship... I suppose that depends on your definition of betrayal. I also guess the mystery aspect and all the clues we meticulously throw out along with the red herrings aren't for everyone. And I can confirm there is more than enough to deduce the mysteries at this point. You are also making an assumption here I want badly to correct, but since it involves a possibility I haven't seen anybody here come up with yet, I think I'll just leave it as a surprise and further tease lol.
I thought we'd covered nearly all the theories at one time or another. So... are you suggesting Francois is actually the MC's mom who faked her death, underwent gender reassignment surgery, and instigated a homosexual affair with Donald in the hopes of tricking him into giving eir the inheritance e felt e deserved? I certainly didn't see that coming!
About Jolina, she's always been among my main suspects as not so much as Dizzy herself but somehow in ligue with her. Yet, in case she's D. in person, i don't see how Donald would have given that nick to a smarth woman like Jolina. Maybe he never meant Dizzy as low intelligence person, but rather clueless or confused by some specific circumstances. Jolina might have been a wannabe enterpeneuse for some time but she never had "the lobes" as a ferengi businessman would say.
Well, Donald was an asshole. It's always possible he would have interpreted Jolina's desire to make something of herself as a dumb broad playing at being an adult; he's not the most objective observer.
That said, while I find Jolina extremely suspicious, I can't quite see her being the third heir. First, because at no point has she ever referenced the inheritance, even while she's preparing to sell her apartment and liquidate her business. Sure, she could just be a fantastic actor playing the long con, but that's hard to square with the way she almost confessed something to the MC after the scene with Jenna in Episode 20. Second, because she doesn't seem to fit the way Donald described her. There's no particular reason for Elaine to hate her, for example. Nor is it clear why she would merit consideration alongside the MC and Elaine if all Donald ever saw in her was 'Dizzy.'
I still think the most likely suspect for the gold digger is Bella. It explains some of her extremely odd behavior, it tracks with Elaine being furious when she learns, and it requires no convoluted coincidences to explain how the affair started. It also gives her a plausible motive for hiding her status from the MC beyond will conditions and/or avarice. If we assume Bella and Jolina are working together, it even explains some of Jo's red flags. The only major downside is that Bella's a rather obvious candidate and it's tough to believe Elaine's detective couldn't turn up any evidence of Bella's affair. But even that can be explained if we assume Elaine is the one who has read the will and simply playing dumb to deceive Bella.
Personally, I'm just not worried about the gold digger. Most of my MCs already know they won't inherit anything so it's a mostly academic issue. Playing kingmaker with his portion of the money might be worthwhile, but I'll deal with that when I learn the details of what is and isn't possible. I'd also be perfectly happy to arrange some sort of deal with one or both of the others if they were interested (and seemed trustworthy), but again, no sense dwelling on that before we know what deals are on the table