This happens with male protagonists frequently as well. You see in children’s stories like authors Lloyd Alexander, Roald Dahl, Lewis Carroll. There are also modern examples like almost every Gaiman book lol, Fairy Tale by King or Blake Crouch.
Iirc, there’s an entire genre of Manga dedicated to this.
But I see what you mean about it being more young girls in western fiction. I always figured it was to subconciously make our lead more vulnerable or innocent as some sort of foil to the environment.
Well there are a few actually! 11/22/63 has a portal, with various in The Dark Tower. But you probably are thinking of Fairy Tale