See Chapter "Vol. 6 Ch. 28.2" on Mangadex for those who forgot about the people kumo rescued.
That chapter happens after escaping the lava layer and beating a half dead fire dragon, but before dealing with the recent major enemies ( like mother kumo/earth dragons/escaping the puppets )
I'm gonna put on my detective hat and guess how the Prince might get pissed.
We already know the Prince thinks blondie is sus from the way he asked her what book she read to figure out the last problem.
We also know that there's a law that was overlooked by Marie that states gold or valuables...
I'd imagine he's using the term "wife" like the way a guy would say "dear" in english
maybe if english had a word that means a cross between "dear" and "milady" or something but i dont think that exists