Just watched the 1987 Stuart Gordon horror movie Dolls for the first time, and it occurred to me halfway through that it was a pretty good Girls Underground example. Little girl Judy and her distant (and remarkably callous) father and stepmother end up stranded for the night at the home of a very strange elderly couple and their many, many dolls. The old man gives Judy his handmade Punch doll (get it? Punch and Judy?), which becomes her first, if silent, companion. Then another stranger comes knocking at the door, and he ends up as a sort of second companion – the only one willing to entertain Judy’s stories of murderous “little people.”
There isn’t a single, concentrated adversary, but rather a host of evil dolls (well…. are they really evil? They only kill the bad people there, after all), but Judy does end up facing off against them alone, when she confronts them and calls them “bad dolls!” and must rescue her companion in the process. The story is missing the normal level of volition from the protagonist, in that Judy is just taken along rather than making her own decision (or mistake), but it gets a bonus point from me for involving an actual descent underground initially (as they enter through the basement).
This is also an excellent example of a Girls Underground story taking place entirely within a house, which happens now and then.
As a sometimes-campy horror movie, I enjoyed it quite a bit, especially since (as I’ve said elsewhere recently) dolls are creepy.