Okay, I just did decrypt the files to check this and i remembered this:
In original game MC asks Valerie/Mom to keep his identiy secret, because he is afraid his past would have effects on his new live ... so someone could find him by coincidence.
So I had to maintain this idea. So even with my incest patch for this game, no one knows Valerie is MC's Mom.
So it's not wrong Emma calls Valerie his landlady.
That way in the original game some things can change. But if the true identity of MC remains secret then it is easier to simply continue the incest patch. Fortunately the game is easy to patch, because the dialogs are very easy to adjust

I still look through the files again and see if there are some dialogues can be made better.
But I am very confident.
The basic idea in the game is anyway very well incest suitable, because it is so that Valerie knows him from before when she was still a social worker.
With the incest patch it is now just so that mother and son were separated for a very long time and here now some real life mechanisms of incest can work.
On the one hand it is so that one looks for genetically similar partners, and genetically more similarly than the own relationship is nobody.
However, Incest is genetically regarded badly for the evolution, it has the nature so arranged, that usualy one does mate in the own clan or pack or with those with which one grew up!
But if relatives were separated from each other for a long time, the inctinct to reject the own pack often does not work anymore and the genetic narcissism can dominate.
If you read reports about true voluntary and consensual incest, it is almost always the case that the people involved have not lived together for a very long time and had no contact with each other.