I had a slightly better result than yours, however I cheated by using the classical "Refine Edge" method. Kindly check other post here…Still having trouble with select and mask
Here is the mask
and here is the result with black background. Note, I applied Decontaminate Colours too.
The refine edge brush can work well in S&M - but decontaminate colours does not (IMO)
Below was S&M to mask then two layers above - one set to colour blend and the other to luminance - both clipped to the masked image. Then some light painting with image colour and luminosity to blend the edges. The luminosity layer is often needed when going from a white background to black as fine hair is almost transparent and just looks too light when the background is darkened.
Finally, I sharpened up the edge of the mask in a couple of places using a black/white brush set to overlay at 50% opacity and painting the edges.