There is another Davidson pattern that is similar in style, and I have also seen it sitting in a metal holder and on each side of an old mirror. That particular pattern is shaped like a vertical cornucopia. As more than one pattern was made and is mounted to the frame of a mirror (and the cornucopia does not lend itself in shape to being used to hold cosmetics), it might just be a small posey vase to brighten up the bathroom. The mirrors I have seen were large enough that it might have also been used in the front hallway to check appearance before leaving the house. I personally think the way I have seen it mounted on mirror frames is that it was made as a small posey vase, but alternate uses could naturally be found. The one original mirror I saw (complete with brackets) had a vase on each side of the vertical frame, about 1/3rd way down from the top. That positioning would also suggest it was for flowers.
Mr. Vaseline Glass