1.) The homewrecker who has relations with married or attached men.
2.) A woman with power and authority, having complete control of a household, business establishment and employing help. ‘Mistress of great fortune.’ 'My mistress wouldn't be caught dead in those fugly garments!'
3.) She is skilled in an occupation or art.
4.) The master or owner of animals.
5.) British. A teacher or head school mistress.
6.) In the olden-golden days, you would address an unknown female as mistress. In the same respectable fashion one would use the term, 'miss'.
While the men of the world were fighting on the battlefields, these women wanted to do their part to help with the war. They were a troupe of TNT shell makers during WW1. They were nicknamed canary girls because of extensive exposure to the toxic trinitrotoluene (TNT) that turned their skin yellow like that of the canary bird.