I tried to tweak the green screen background with the nodes given by gonzalo. Regarding the treatment of the hair, I had to select an “IBK Color” node and choose dark and light colors of G (green) to show as much detail as possible in the hair. I can also use the “Filter erode” to eliminate noise. It’s worth noting that it looks very realistic and I used the Luminance node to subtract the snowflake from the background and place it in the foreground so it looks great.