Stop being mean to me I saved your daughter.

Before you start the quest "Heart of Dibella" Enmon and Mena have fairly rude dialogue toward the player. It's not personal they just don't like outsiders. However during the quest you rescue their daughter from a forsworn cult that kidnapped her. And take her to serve as the Sibil of Dibella. Something her father is very supportive of. (Her mother has no dialogue on the subject). He's very nice to you and supportive of your actions during the quest. But once the quest is over. He goes back to being rude to you for no reason. Which makes zero sense.

If he was opposed to his daughter being Sibil I would get it. But he was very supportive of the idea. Not only that. His dialogue is the exactly same as it was before the quest. Essentially treating the quest like it never happened. This mod is pretty simple. All it does it make raise Enmon and Mena regard to the player from 0 (acquaintance)  to 1 (friend). Once the quest is complete.

This will block all their rude dialogue as it all conditioned on the player have a relationship rank of 0 with them. And give them generic friendly greeting toward the player.

Can I install this mid game?

Yes and no. If you install it after already completing "The Heart of Dibella" it will do nothing. If you install it mid game before doing "The Heart of Dieblla." It will change Enmon's dialogue but not Mena's. As we don't know Mena's opinion on her daughter becoming the Sibil of Dibella I suppose you could argue that immersive. It will only fully work with a new game.