Answer: zero.
Justification:
The downward velocity of the sky diver just before starting to fall is zero, assuming that the helicopter is not moving but just hovering.
Before starting to fall, the velocity of the skydiver is the same of the helicopter, which is zero. It is only, once she jumps out of the helicopter that her weight is not supported by the helicopter and so the gravitational force of the Earth attracts the skydiver and she starts to gain velocity at a rate equal to g (around 9.81 m/s²).