Noise on hair

I made a new render with Natasha in Sci-fi Library project 1st shot, here is the end of it:

Samples are 700 in path-traced and that is already too much I think. All other looks good but the bight hair on her right side is noisy.
It is due to the strong light behind her, I belive.
I tried to play with all settings for that hair material but had no success removing this noise. What can I do here?

Moving the light and shaping it is one option, but first I want to ask this :)