There are two singers with this name 1.an American R&B/pop singer 2. A pop singer from Argentina :

1) Sybil (born as Sybil Lynch in Paterson, N.J.) is an American R&B/pop singer, an excellent vocalist and one of the finest among disco divas, who has been recording since 1986.
She is best known for her covers of Dionne Warwick's hits "Don't Make Me Over" and "Walk On By".
However, it was when she signed with the music UK producers Stock Aitken Waterman on label PWL, that Sybil had the biggest success, and was particularly popular in the UK. She had two massive hit in 1993: The first, a West End production of "The Love I Lost", originally a hit for Harold Melvin & The Bluenotes, and the second, "When I'm Good And Ready", an original song written by Mike Stock and Pete Waterman after Matt Aitken had left the company.
Her most successful album was also released that year: "Good n Ready". The same year, her US album Doin' It Now was released.
Most of Sybil's hits have been covers of standards, and her career gradually evolved from dance towards soul/pop. Her last single to date was released in 1997.

2) Sybil a pop singer from Argentina
Born in 1984, she had only one Successful single called «Circus» which was showed only at MTV Latin america