Green’s Dictionary of Slang

1. (US) a female detective.

1884

N.Y. Mercury June in Ware (1909) 89/2: The confidence queen of Miss Caroline Hill revealed that lady’s stage qualities to great advantage.

2. (US campus) a female confidence trickster.

1881		Baltimore Sun (MD) 4 May 1/3: A Confidence Queen Indicted.— The Richmond [...] grand jury have indicted Bertha Hayman, the accomplished beauty, who has rendered herself so notorious in Canada and elsewhere.
1888		L.A. Dly Herald 14 June 5/1: Bertha M. Stanley, the confidence queen, took much fresh air after her release.
1902		Century Mag. 63 314: Sez Alderman Grady To Officer Brady: ‘Where 's Katie Macready, The Confidence Queen?’.
1905		Salt Lake Tribune (UT) 15 Jan. 21/5: Bertha Heyman, alias 'Big Bertha,’ was another famous ‘confidence queen’.
1911		Arizona Republican (Phoenix, AZ) 17 Dec. 18/3: Confidence Queen [...] Eighty-two-year-old Ellen peck [...] has served about two years of her ten-year sentence for swindling .
1921		La Meschacébé (Lucy, LA) 21 May 7/2: Do you think [...] I look the least bit like a burglar’s pal or a confidence queen?
1934		L.J. Vance Encore the Lone Wolf 55: He was born with a pack of cards in his hands— out of Natchez Nell, the confidence Queen, by a Mississippi River steamboat gambler.
1997–2000		Da Bomb 🌐 7: Confidence queen: A female swindler.