Silver hair even though it was mentioned that in the Frozen Isle that hair is usually black like Isaac's? Either she is the princess or the princess used an aide to do the writing and sent her off to Aitheria to learn about it.
It would be funny if that’s the princess’s retainer, also a royal-blooded of sort, who writes all things for the princess, and somehow Arnoux ended up marrying her instead.
Bro that's your hot ass wife who came to nobu based on what you likely told her about tempura, and so shes learning how to cook it for you as a surprise for your wedding with her you lucky bastard
Peoples hair colour can change with age(not just go gray), a lot of babies have very light hair when they are born and it gets darker as they grow older.
I'm guessing her hairband which has her family symbol is probably some kind of magical item to hide her real appearance.
Some kind of 'hide your true appearance except for the man of your choosing' type of custom to avoid the abductions.
Even more so with the mention of Norse-related stuff earlier in the chapter, they do have things like selkie there after all.
Meanwhile, in a different series.
There's both:
Bride Stealing Ditter (pretty much one-sided feeling)
vs
Bride Taking Ditter (the parents disapprove, but the bride want the marriage)