Yeah...I don't get it.
Firstly, why does it seem like the royal family has anything against the family of spirits and effective gods? They're the one scrambling for any cards to play while the hero's family has basically every possible trump card. Heck, if it's such a problem, I don't think it'd be too difficult to outright usurp the royalty.
Next, why is it such a bad thing to let her meet the royal family? They certainly won't have the power to forcibly bind her in a contract or anything as long as she isn't tricked-which she should be clever enough to evade. She isn't even raised a noble, so I think she could get away with insulting that king to his face.
And lastly, the bride. I mean...I'm not gonna say she's not at fault at all, but she honestly hasn't done anything either. If you're gonna condemn someone for feelings or thoughts they can't control, then it feels like a lot more marriages would end before they begin. Not to mention political marriages where love isn't involved at all.