It's not even a question of time in this case, but choice, I explained a few times now (meaning politely saying a lot of times), first the game is about Myriam, then each character has already its purpose in the game, always revolving around Myriam or revealing another side of Myriam, and for Katherine it's all about love and being a positive constant in Myriam's life.
Katherine is an important beacon of positive feeling for Myriam, so no corruption on that front, though it doesn't mean there won't be any naughty situations, but just that it will always end with a positive outcome relationship wise between them.
Though yes it could be argued Myriam could "corrupt" her daughter with love and good intentions...
So I understand it can be disappointing as a player when you want to see some characters in some specific situations, but there is already quite a few kinks in the game, and yes, I'm also limited in time I have to work on every plot lines already started.