If someone appears in your dream and is indeed identified as either your or someone else’s mistress, that person is a character aspect of your own personality.
The representation here is about the desire to connect to intimacy without emotional risk. [1]
If you are single and have this dream, it suggests that you or someone in your circle is being lured or tempted into some negative activity.
To dream that you are someone’s mistress indicates your desire to get things without working for them. [2]
concubinage, being member of a: have little self-respect nor care for public opinion.
having a: great danger and dual life wil bring public disgrace.
household recognizing a: old enemies wil be faced by entire family.
of a: security needed to keep true motives hidden. [5]