Now, someone might be engaged at that age, though even that would be exceptional. That’s the kind of thing a Kevin’s Famous Chili they call me one-take wonder vintage shirtl family might do, laying down a marker as part of a scheme to create or maintain an alliance with another royal or important noble house. Since it’d be a somewhat exceptional event, there’s not really a standard operating procedure, but it seems likely that she’d stay with her own family until she was old enough to marry. Indeed, depending on circumstances, she might stay with her family even longer. There are cases where people were married by proxy because for one to travel to the other was too difficult. Some agent would stand in for the other party for the purposes of ceremonies at both ends so they could legally conclude the marriage without ever necessarily having seen one another.