Well, we know that the gold digger knows the conditions of the other two recipients. Now assuming that it really is Bella, she'll be aware of the fact that a certain point, the MC will have to make a decision about the house and that it's Elaine's condition.It's definitely shady, but that cuts both ways. If the nebulous conspiracy had that video the whole time, why wait to show it to the MC? If they only created the video once it was clear the MC knew about the forged emails, how did they create the video? For that mater, what do they expect to accomplish with it? Why give the MC evidence he can take directly to Elaine? It would have been just as effective (and harder to backfire) to have Jolina claim to recognize Elaine when the MC showed her picture the first time.
We know something weird is going on, but I still don't think we have enough information to speculate productively.
So why would she want to turn the MC against Elaine? Simple, even if it has nothing to do with her own will condition, by getting rid of Elaine she increases her share of the inheritance by 50%. And if she can knock the MC out of the picture, she'll get the whole shebang.
Why hold on to the video for so long? Because if she knows the will conditions, she might also know the time frame of when the MC has to make the decision. If the MC had the video earlier, he could've confronted Elaine and she might have been able to set him straight. They purposely waited to give you the evidence at the last minute and even then Bella told you to not confront Elaine with the footage.
And it's not impossible to deep fake someone's face accurately enough that it might fool some people, especially with a low quality footage. Someone like Jolina, who has shown that she has some tech skills, could pull it off.