It is inspired by the story of The Supremes, but it's still a fictional piece.
Florence Ballard was never the lead singer of The Supremes. If you listen to their earliest recordings, back when they were a foursome known as The Primettes, Diana (then known as Diane) Ross was nearly always the lead singer, although Florence and Mary each had their occasional solo. The primary difference is that their backing vocals were featured much more prominently. They also stood alongside Diana when they performed live. As they became bigger, the girl group phase began to wane. Ross' vocals were more dominant on the recordings and she stood in front of the other two when performing live. Florence felt that they were being phased out. She wanted solo lines in songs, as the guys in The Temptations had, but Berry Gordy was not interested in such an arrangement. She gained weight in her last year with The Supremes (although she was never as big as the Jennifers Holliday and Hudson) and became erratic. She drank a bit and could not handle her liquor. She would miss rehearsals. She once missed a show and Diana and Mary performed as a duo. She was spoken to and told to get it together, and she knew that Cindy Birdsong, who had filled in for her when she missed an engagement at the Hollywood Bowl, was rehearsing the stage act in her absence. She did make an effort to shape up, but when she arrived in Vegas in July of 1967 to see them now billed as Diana Ross and The Supremes on the marquee, she lost it and performed poorly. That turned out to be her final show.
She had recorded the songs that were on the first "Diana Ross and The Supremes" album, "Reflections", but Cindy Birdsong was credited. On nearly all of their later recordings, Diana sang leads and Motown back-up singers The Andantes provided the support. Mary and Cindy usually only sang live. Florence's more robust voice was plainly missed, but if you listen to her solos you will realize she was no Effie White-style powerhouse. She was just a good singer who tired of her increasingly reduced role on the world's stage. Her own unpredictable behavior had more to do with her being replaced than any other factor, and I doubt anyone was very happy about replacing her.
The tragedy is that she was bought out for very little money, and her release stipulated that she could never promote herself as an original or former Supreme. She was never able to get her career off the ground and with a family to support she went broke. It was a shock in the early 70s when she resurfaced on welfare. She seemed on the verge of a comeback, and then, out of nowhere, she died.
This is my favorite lead vocal of hers, from the album "The Supremes Sing Sam Cooke." I hope you like it:
https://www.youtube.com/watch?v=EBE367JNWSU