To be fair here Rozemyne’s reaction to the suggestion she and Ferdinand did the deed Pre-Marriage would elicit a similar reaction in our world even as recent as 100 years ago so that’s just perfectly understandable. Although I think it would be best for Rozemyne and Ferdinand to keep the details to themselves, I suspect a lot of what they did would be considered more than scandalous by the other nobles.
I put the focus on the pre-marriage part simply because underage marriage does not seem particularly rare among the nobility in Yurgenschmidt, pretty much how it was in medieval times here. I highly doubt Rozemyne being way too young for marriage by our standards elicits much of a response beyond “might be a bit young that one” from most of these nobles.