Eh. "Not realistic" conflicts with a number of happy throuples and polycules I know IRL. That said both in writing and IRL its a delicate issue that needs careful handling. I think the author could do it but you're right that 1 winner or power of friendship are more likely.not realistic in the slightest aside from porn or fantasy world logic. Could be viewed as an even bigger cop-out than #2 if handled poorly because while that is "we avoid the problem and don't deal with it" this is "we choose the most ridiculous possible answer and ask people to accept it in spite of its obvious flaws"
If one girl "wins" I suspect they'll be official girlfriends in sequence before one gets to be the final one and they all stay friends. My grandparents had a relationship like that lol just with marriage involved.