Cut The Throat That Defends You?

I'm trying to find the name of a horror movie from the 1970s. The most prominent part of the film comes at the end.

A little girl ends up being pretty murderous (not The Bad Seed). One woman refuses to believe the little girl is evil; the film ends with the little girl sitting on the woman's lap, then the camera pans from behind the woman seated in a chair, to the front - it is then you see the little girl has slashed the woman's throat.

What is the name of this movie?

Helane