Yes, Ma'am is appropriate or Mistress, Lady is also very fitting, but I will let you select which one feels right.
It is Mistress or Lady that feels right you know.
Only 100? Are you certain you are a witch? Perhaps you are something else entirely, have you considered this? It is definitely for the best that you are something else. Let's see. Banshee? Are you screaming a lot do you think?