It is perfectly possible that your remember correctly, though for the "getting caught" in itself (not by Katherine), I remember Zorlun had not excluded completely the possibility of something happening when Myriam goes to the veterinarian clinic, and if "something" happens, would not be surprising if involved the dogs, but would also not be suprising if the veterinarian caught her, it probably is not a huge clinic.
About poor Katherine, "non entity" is really harsh. She actually has a an important role in Myriam's life, and therefore, in the game dynamics - it is only that the role does not include, and actually excludes, getting in sexual escapades like the ones of the mother. It is a bit of a pity in kinkiness, but it is also part of the how Zorlus tries, despite giving the opportunity for plenty of sexual activity for Myriam, to keep the game from becoming a "fuckfest".
About the future game, I may be wrong, but I think Zorlun already said he plans to have different characters, he may have a cameo for Myriam, but that would be it, at least as far as I understood it.