Theory of upcoming updates
according to game story:
Amy content
Laura's content
School content
Content of Tyna and the gangs (the Pussycat Fights)
Sarah's content
Lucy's content
The order of the girls in the house seems to me to be the one indicated by what they have shown so far with Lucy.
1-In the content of Maria it is implied that she already knows or intuits about Maria and Mike.
2-She has not had sex for a long time and she is visibly frustrated and jealous when Maria is having a good time with her "unknown" partner.
3-Lucy currently has a slight "curiosity" about her son's "package".
Following that line that little by little she finds out that her son is having sex with the girls they live with and is more tempted to the idea of fucking her son.
I think Sarah would be instrumental in inciting her into incest.
Surely what happens is that she takes it very badly at first. But when she sees that they have a good time and supported by the "sexual freedom" law, close her quest to fuck her.