If I remember correctly, it was revealed in EP-20 by the lawyer that someone knew about the will conditions ahead of time. That could possibly be Elaine since she would potentially have access to the will...if the MC's father left it out by accident - or not.
While Bella did say that Elaine threw the MC's stuff to the curb...Elaine told the MC that she would, via email, in 3 days if he did not come and get it. So, there is no real reason to doubt that she did and Bella was doing the MC a solid.
From the lawyer we know that there ar 3 people in the will, the MC Elaine and...
The lawyer also tells us later tha one of the 3 knows everything about the will and seem quite cold and determined to win.
In episode 20 we know the Elaine sent the false email.
Knowing that Elaine lived with the father Don and could have acess to his office and maybe could have heard him when he was recording his will, it's quite logical to think that she is the one who knows all about the will.
We know that Elaine visited many lawyers to get infos about such a strange will.
At the beginning i totally rejected Bella and Elaine because it seemed stupid to do othertwise!
So it's only much later that i started to get friendly with them and i started the guilt path in the last chapters.
So is Elaine the evil one, maybe not, i guess she is really worried to loose everything because she knows all the details, mostly she absolutely wants the house, i guess that's why she sends the MC away and make him go to Monica because she knows that she will loose the house if he accepts the will conditions.
At the end of chapter 20 i was able to seduce Elaine and fuck her balls deep once i promised her that she could keep the house any way.
So who's the third one ?? Bella i guess, she seems to have a strange behaviour, first she comes to Monica's with MC stuff before the 3 days that Elaine gave him.
Then when the MC and Jenna tryied to hack Elaine's PC she seemed to be aware of what was going on and went to Elaine's room with no reason to masturbate on the bed and just after tried to seduce the MC right away.
Later we learn that she is spying her sister and tried to take the MC on her side.
Knowing what kind of sick prick the fater Don was and his hatred for family relations, i guess he wanted to separate Elaine and Bella. I guess he had a place in town where Bella was living completely depending on him and when he died she was homeless and forced to go to her sister's house.
So i start to see why Elaine seems so worried, she knowns everything, she has to send away the MC, and i guess that there is a condition that will seperate her from her sister for a long time and she gets really desperate about this. Finding herself all alone with no familly.
That father don must be really sick and has a specific hatred about family realtions and wants to separate all his relatives.
He dispise his son, Elaine and Bella because they depend on him and are not independent and strong, for him they are bugs living from his crap and want to teach them a hard lesson.
The old prick wants to crush the cockroaches that are running on his coffin!