What is a lesbian mistress?

Answer 1

A lesbian mistress is a woman who is involved sexually with another woman who is in a relationship. A mistress, in general, is the "other woman" that someone, man or woman, is cheating on their partner with.

Answer 2

A lesbian mistress is a woman who is in a romantic or sexual relationship with another woman outside of a committed partnership. She may be dominant or in control of the relationship dynamics.