All I remember is a scary woman at the window of a boy around the age 11-14, and I think the window was upstairs. I think he opens the curtains to see her there, which scared my young self. She was dressed all in white with like a white head scarf and you just see her from her torso up, and she may have been called The Ice Queen or Ice Witch? She talks to the boy, and then I believe she magics him a way to her cave, and the boys younger sister tries to save him? It's possible the kids had telepathic powers or something.

It might be from a series called "Into the Labyrinth", but I don't want to buy it unless I know that's it. Might be in the film "The Amazing Mr. Blunden"? Or something else? Open to any suggestions!

The Chronicles of narnia

It was first produced by ABC.in 1967 it was a Ten part mini series.
Then it was produced as a animated TV movie I believe in 1977,
Then it was produced by the bbc in 1988. But it was , The Lion The Witch And The Wardrobe
But this may not be what your looking for.there was a book before this but I don't think there was a movie made it.
Good Luck with your search.