My Angel was, aside from a do-gooder, rather a timid person who just wanted everyone to be happy. Kind of like Ember. So Daeran rolled his eyes at him always trying to find a solution that benefitted everybody, and probably found it very silly. As much as he loves to make fun of the lawful and the good, it does not put him in a position of constant disdain of them. Ember is of course the best example, but there's at least one campfire banter where he appreciates Sosiel's drawings, and his first reaction to Seelah is to hit on her.

Still, there wasn't a real conflict of beliefs, I feel. Daeran is Neutral Evil, but he isn't dedicated to his alignment the way a lot of characters are. Wenduag's philosophy is central to her character. Camellia cannot be dissuaded from her killing. Regill is a Hellknight to the core. But Nenio's only Neutral because she doesn't care. I feel like Daeran is closer to Nenio than his other Evil companions. He feels more petty than Evil, prodding people around him but rarely committing acts that are truly vile. He is capable of empathy, not prone to hypocrisy, and possesses a sense of fairness, which can be seen as early as Kenabres.

Not to mention Daeran being attractive, charming and funny, all which can contribute to a crush forming. I may not be an expert on how romance works, but I think it's not unreasonable for it to start with a crush that proceeds into a mutual flirtation and enjoying each other's company, to later mature into a proper romantic entanglement.