Damn... Ah well. Thanks a lot for answering my question regardless, it's very much appreciated. :)
(After going at it for some time I noticed that the "preggers" with them can't occur normally when losing to them it seems, at least for most cases i've seen thus far. As such, i'm guessing that defeating them instead might be the way to do so, but as my MC is still currently weak, I currently can't say for certain yet)
Pregnancy with them works differently in game, they just spawn a Slime Minion instantly. Though, they can also drop a Slime Core if you defeat them, which lets you summon a Slime Minion of your own. You can also very rarely get a Slime Core from them if you lose to them and satisfy them enough through sex.
Though, if I ever do implement a Slime Heroine, she will likely have a more standard like pregnancy, with the belly and all.
There is no Sex Scene for defeating them. Currently, the only Monster Girl that has a special scene when you defeat her is a Werewolf, the rest don't.
