Betty Boop’s character was actually based by animator Grim Natwick on vaudeville performer Helen Kane. Miss Kane wasn’t pleased… here’s what Wikipedia says about it…

In 1930, Fleischer Studios animator Grim Natwick introduced a caricature of Helen Kane, with droopy dog ears and a squeaky singing voice, in the Talkartoons cartoon Dizzy Dishes. “Betty Boop”, as the character was later dubbed, soon became popular and the star of her own cartoons. In 1932, she was changed into a human from a dog, her long ears turning into hoop earrings.

In 1932, Kane filed an unsuccessful $250,000 suit against Paramount and Max Fleischer, charging unfair competition and wrongful appropriation in the Betty Boop cartoons. The trial opened in April 1934 with Helen Kane and Betty Boop films being screened by Judge McGoldrick (no jury was called). Margy Hines, Bonnie Poe, and, most notably, Betty Boop voice-over talent Mae Questel, were all summoned to testify. McGoldrick ruled against Kane in 1934, claiming that Kane’s testimony could not prove that her singing style was unique or not an imitation itself (a little-known black singer known as “Baby Esther” was cited by the defence as “booping” in song).

Surprisingly, there are a lot of Helen Kane videos on the web… here are a few of them.

Here’s Helen Kane in “Dangerous Nan McGrew” (the name being a take off of the Robert Service poem The Shooting of Dan McGrew)

Here she is performing “I Love Myself Because You Love Me”

Here she is performing “He’s So Unusual” and “The Prep Step”

I can’t find any films or recordings of “Baby Esther,” unfortunately… it sounds like she may have been the original original Boop-A-Doop girl.