All throughout history, even though heterosexuality has been the norm, relatively very few societies have allowed the female partner a true choice in the formation of the couple. This has been so regardless of the average ages of the female partners: young or not so young.
And yet, in the current Weird countries, and increasingly elsewhere, females are having a choice at who is their husband.
There is no reason why girls can't be afforded the degree of choice that women have over their partnerships.
And all the more so for gays and trans. We all know a minority of societies allowed this sort of lifestyles in the open. Even where tolerated, the sort of civil unions (call it marriage or not) now prevalent in the Weird countries have been, while not unheard of, extremely rare. But we have them now.
Again, if it happened for the gays and trans, why can't it happen for girls (and boys?)