Her testimony sliced her family into factions, relegating her to years of exile, and it may have stifled her career. Today, Sparkle is arguably more well known for her public stand against him than she is for her music. And as Mr. Kelly faces new charges of sexual abuse, prosecutors have told her she may be called to testify again.

“I hope they don’t need me,” she said. “But I have to. I have to see this thing through.”

[Read more about the latest charges against R. Kelly.]

Sparkle, whose real name is Stephanie Edwards, was born on the West Side of Chicago, the youngest of six children. (She described her current age as “somewhere between birth and death.”) The family moved to the suburb of Oak Park when Sparkle was 3, and she started singing in church a year later. Encouraged by her father, she and her siblings formed a gospel group growing up. “I don’t know if I ever dreamed of being a professional singer, because I wanted to be a model,” she said with a laugh. “But dear old dad, he was like, ‘No, you get up there and you sing, and you’d better be the loudest!’”

She met Mr. Kelly in 1989 and a few years later, she said, she was singing backup on an album he was producing: “Age Ain’t Nothing but a Number,” by the singer Aaliyah. The album title would soon take on a sinister cast: The year the record was released, a 27-year-old Mr. Kelly reportedly married Aaliyah, who was 15. The marriage was annulled. (Aaliyah died in a plane crash in 2001.)

Mr. Kelly’s lawyer declined to comment for this article.

Sparkle said that at the time, she thought talk of the marriage was a publicity stunt. How could anything like that happen when Aaliyah’s parents and her uncle, who was Mr. Kelly’s manager, were always around? Still, she continued working with him.