[TOMT][Movie] The protagonist wanders into a house and discovers children with fake heads...
I'm looking for a European/American horror movie:
The female protagonist gets lost near a forest and finds a house to take shelter in. Inside are middle-aged parents and their children, ranging from toddlers to high school students. The house is in the forest but not too far from the city; they can still go to the town, and the characters still go out to the market, shopping, etc.
I don't remember why the female protagonist stays there for quite a while, and she starts noticing strange things. The children are terrified of their mother, even though she seems normal. One of the eldest or second daughters sometimes goes out wearing completely different styles of clothing (for example, sometimes office wear, sometimes boyish clothes, sometimes Barbie doll clothes, etc.).
Later, the protagonist discovers that this isn't her real family. The children were lured into this house, and the mother took their real heads and hid them. Their normal appearance is due to the fake heads their mother gave them (but they still look like normal people; when hit or bumped hard, the heads fall off or get dented like doll heads, so the children sometimes take them off and swap heads with each other to play, and the female protagonist accidentally discovers this because their clothes are different). Without their real heads, they can't escape the house.
There's a scene where two children, about 8 or 9 years old, a boy and a girl, are playing head-swapping. After swapping heads and playing together, they suddenly start arguing, or something, because the younger sister refuses to swap back to her original head, so they start fighting.
The older daughter is the most recent victim, so she's still struggling to escape (she uses a different head each time she goes out to play for different purposes like going to school, working to earn money for the family, etc.). Later, the female protagonist learns that her daughter is plotting to wait for her mother to take her head so she can find the hiding place of her own head and escape (the female protagonist has some special quality that prevents the mother from carrying out her plan).