Problem
The girl was shot against a very crowded background. The fair hair, is in many places, found on a similarly colored background. What's more, the hair is very fine and in tails and looked like it would require fine tracing work to cut out, what with with individual hairs going in every direction.

Solution
The complex mask was put to work here and a lot of fine tuning was also required.

I had to very accurately remove as much space between the hairs as possible in order to completely eradicate the background...and it worked!