Here are my thoughts on Daughter's mom and variations how Father is actually the bad guy in this game:
I believe that Father's relationship with Rachel, and the reason for the breakup, can mirror the outcomes in this game. This leads to the question of what actually did happen between Father and Rebecca. Father says she accused him on multiple times of having sex with Rachel's best friend. Father denies this to Daughter. Is what Father says the truth or a lie? Did he or did he not sleep with Rachel's friend? What follows is five solutions to the Mystery of Rachel.
(1) Father is Telling the Truth - (The FAITHFUL HUSBAND) - This is the vanilla outcome in which everything Father said is true. This is the character that Daughter will fall in love with - faithful, romantic, caring, and protective. This is the kind of man Daughter has always been looking for and would even go so far as to marry and have children with. "Dad, I want to give you the family you and I always wanted."
(2) Father is Telling a Lie - (The LOTHORIO HUSBAND) - This is the Father who accepts kisses from Elena and agrees to make out on the couch with her. This is the Father who keeps a naked photo of Elena on his phone. If Father was really telling the truth about Rebecca, why is he so easily seduced by Elena? Now we could play the game without going down the Elena route, but, really? The end result of this Father/Daughter relationship could be varied, depending on how it is played out by the characters. Does Rachel continue to insist on the Father's affair(s)? Does Rachel's old girlfriend show up and cause a stir? Does Father eventually admit to that affair?
(3) Alternate Events - (RACHEL AS HOT WIFE) - In this version, Father and Rachel had a relationship where Rachel could have other lovers and the Father did not. In this version, while Father never did stray, Rachel's continuous disbelief that he was not after sex with other women when she's had multiple relationships caused her to truly believe he strayed. (Or perhaps he eventually did stray. If this was their relationship, would Father bring the same to his relationship with Daughter?)
(4) Alternative Events - (RACHEL AS CUCKQUEEN) - The opposite of #3. In this set of events, Rachel would have found Father's affections straying to her best friend more than to her. Seems a little sad and mean for the protagonist of the story, but maybe Dad is an ass.
(5) Alternative Events - (INCEST) - In this scenario, Rachel is lying about her best friend and Father for another reason: she was afraid of the safety of Daughter from Father and sex. This could happen in two ways. First, Rachel and Father were involved in mutual incest role play as Father and Daughter. This was fine until Daughter got to age 8. Then the worries of Rachel exploded to the point she either made up the story about her friend or Father was driven to the arms of her friend due to their tensions. Second, Rachel actually had an incest relationship with HER father, which she brought into the role play relationship with the Father character, resulting in the same outcomes as above. Frankly, the incest scenario would be the only one I could see where Rachel might condone the F/D relationship and might even join in.
So there it is - five different alternative prior events between Father and Rachel leading to their breakup and then having repercussions in the relationship with F/D. In essence, this game is not just a relationship story between F/D, but it is also a mystery - a mystery as to what a happened between F and Rachel, and, ultimately, a mystery as to who the Father really is as guided by the player.
The alternative endings could get all played out at the last chapter, with previous event choices weighing in favor of one outcome or another.