The cat hierarchy changes with time as the kitten grows up. That may be what this is; they are just resettling the order of things. Is either one an alpha / dominant one? You can tell by head size. An alpha male has a much larger head than most cats. Ditto an alpha female.

You say she is still scared of him, but then say she approaches him to groom. Well, then she isn't too afraid of him, is she? If she backs off when he looks at her, that is good. They understand each other and no fighting involved. As long as they aren't into bloody battles, I would wait and see if they work things out between them. they just may not be cuddling buddies for now.