Much to my shock she had utterly vanished!
All ready to insert a clone in the place of the MIA orc, I fired my game back up... walked to the necromancer's customary area.... and there she was... standing in the corner as though she had never left!
So, there was no need for me to mess around with the console after all.
Now, I know it is a documented bug that Sharn sometimes pulls a vanishing act.. but has anyone else ever had her magically evaporate and then reappear again?