A man going south on a busy street pass the driveway where he is
suppose to turn right into, so he looked over his right shoulder saw
that it was safe for him to reverse and while in the parking lane (or
the shoulder of the street) he began to reverse, at the same time a
woman going north (the opposite direction of the man before he began
to reverse)who also wanted to make a left turn into the driveway made
a left and the man reversing struck her car while he was reversing
pass the driveway.
Who is at fault? Is it illegal for the man to be reversing on the
shoulder of the street where it is legal to park or is the woman at
fault for not yielding and making the left turn into the driveway only
when it was safe to do so.

The person driving backwards on the shoulder is clearly at fault.