She's a straw-feminist (and misandrist, not to be confused with the former term) bank robber and master thief who convinces Blossom, Bubbles and Buttercup into being straw-feminists in order to have them fight against men and boys so she can continue to rob banks. She steals only Susan B. Anthony coins since all other forms of money have men on them. She, at the end of the episode Equal Fights, is promptly beaten up and taken to jail after the sisters tell her who the suffragist, Susan B. Anthony, really was. Unfortunately, after this, she only has a minor cameo in the series finale of the show.
"Femme fatale" literally means "fatal woman" in French.
The symbols on her outfit and weapon are based on the symbol ♀, which stands for Venus, coming from the mythology goddess Aphrodite, and extending into the meaning of the female sex.
When she's wearing convict stripes at the end of Equal Fights, we find out that she has blue eyes and she complains that the horizontal stripes of the uniform make her look fat.
Also in Equal Fights, she makes references to Princess Morbucks (as "that little brat") and Sedusa (as "the chick in the underwear"). Princess and Sedusa are two of the major villains in the series.