@Robbini
I think she could even be from religion, like holy maiden having some prophecy or something.
Noble-wife would have made the only sense when her house had basically dead male line and she was ordered by a King (get rid of her without killing - traitor family, etc), otherwise, nobody would want to live in some remote place which had nothing to offer. So far MC is noble in just a title, he has no people under him and so far no riches were discovered in the land.
Royalty is kind of unlikely, fellow knight seems more plausible.
One more possibility is a merchant's daughter. It would be a move to gain influence precisely because of the title.