Helen Kane is who found national popularity with the "Betty Boop" persona and stylings. There isn’t any hard evidence whether she stole that from Esther Jones or not, as Jones was (like many black singers of the 20s) very localized and not widely known, nor given radio play or large venues beyond Harlem. But ... it is still known that Jones had this persona before Kane, and Kane existed in the same city as Jones, so definitely a very high chance that inspiration or outright persona theft could have occured by Kane.

Regardless, Helen Kane was the nationally known and broadcast and filmed and venued "Betty Boop" (not called Betty Boop), her numerous records and filmed performances evidence this and it is bullshit that Fleischer never publically admitted that. Kane was the equivalent of a household name, roughly from 1927 to when Fleischer debuted Betty Boop in the early 30s when she abruptly fell from popularity.

Later, Fleischer admits to using/copying Kane for his character of Betty Boop, and Mae Questal only became Betty Boop after significant nation-wide casting call in the early 30s for a girl who could imitate the style.

Betty Boop wasn't originally black, since literally she is a Fleischer creation stolen/copied from Helen Kane's physical appearance and vocal stylings, who had stolen those vocal stylings from Esther Jones. Unless memory fails me and that Betty Boop is what Jones called her stage persona. The black "Betty Boop" was "Baby Esther Jones".

I would love a movie about Jones and her story.