Mistresship or Mistressship: How To spell?
The word Mistresship is misspelled against Mistressship, a noun meaning "Female rule or dominion."
Mistressship has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings mistre & ship which should not be misspelled with single 'S'
Wrong Spelling:  mistre-s-ship  Correct Spelling:  mistre-ss-ship 
Find more wrongly spelled words of Mistressship to spell it well.