Well, here's my humble contribution to the modding community after playing around with Python a couple of hours for the first time. As I'm completely new to Python and to the game code, I leave no guarantees here, and it can probably be done better if you know what you're doing. Use at your own risk. Thanks to whoever made the Bree gamer/maid mod, which I used as a reference for the event lookup.
TLDR: It's two separate mods, one to set fertility of girls to 100% instead of a monthly cycle, and another to prevent Kylie from relapsing after you've completed her redemption path (with taming harem support). Just put them in the "game" folder with the rest of the .rpa files. If you want to see what they do, you can just open it them up in notepad.
More details below...
The first is a simple change to the fertility property which basically makes it always 100%, unless on the pill in which case it's 0%. Originally it was just 100% since the rest of the code looked like it'd handle the contraceptive scenario, but after some testing it resulted in pregnancy in some situations anyway that I'm not sure why (for Palla specifically), so either it's a base game issue that gets exaggerated by the 100% fertility, or there's something going on that I don't understand. Either way, should not make a difference, and you should be able to disable pregnancy through the in-game contraceptive policy as per usual.
The second does two things, which is to add an event to lock Kylie's yandere max and current to 0 after you have completed the redemption path (just interact with her one more time after the final conversation that sets her max love to 100, without getting her yandere to 25+ before), and to remove the yandere >= 25 requirement for initiating the taming harem which would otherwise prevent that from forming without knocking her back to the yandere path. I have not tested this one extensively, but it seems to work for the expected cases at least, and I don't think there are any further events that can trigger without her yandere being increased beyond the max cap (unless you use the console or something, in which case you're on your own). Locking Kylie yandere might screw up saves, but I think it should only trigger after her story is completed (minus the potential relapse, which will be disabled).
