either way its a glitch since if you get to 100/100 you should win and if cheemy goes to 5/5 after you get 100/100 it should be overruled by you winning since it makes the player feel like they unfairly lost [because they did] and it also makes the game look bad so yes it is a bug and you are wrong
What was the "mission objective" of the setup? Reaching 100 hornieness, no matter what. Or was it having fun under the eyes of Cheemy without her bonking you.
To tell it in fluff, your goal is to make the other toon so horny that she will follow you to your room for more. But alas, Cheemy is suspicious and will not allow it, if she thinks you two will do nasty things. So even if you reach max horniness, if Cheemy bonks you, you cannot reap the fruits of your achievment, because "you ded".
While overanalyzing silly fun games is fun, it only were a bug, if it were established that the only thing needed to win, is 100 horny. But with the "ded" thing, I believe it is quite established, that this losing condition will trump the winning condition.