Taffy Nivert is her name.
She and Bill Danoff made up the folk group "Fat City", later to become "Bill and Taffy", which played in the Washington, D.C. area, where Danoff attended Georgetown University.
One night in 1970 they shared the bill at a folk club called the Cellar Door with John Denver, who'd just released his third album, called "Whose Garden Was This?"
After opening night, the three piled into Bill's car and headed back to his place for an impromptu jam. On the way, there was a car crash, in which John's thumb was broken. He was taken to the hospital, where a splint was applied.
By the time the three of them got back to Bill's house, Denver was, in his own words, "wired, you know". Bill and Taffy told him about a song they'd been working on for about a month.
The inspiration had come while they were driving to a family reunion of Taffy's relatives in Maryland. To pass the time en route, Bill had made up a ballad about the little winding roads they were taking. Later, he changed the story to fit that of an artist friend who used to write Bill about the splendors of the West Virginia countryside.
The original second verse of the tune was quite risque, making reference to nude women and such - so Bill and Taffy figured their song would never ever get played on the radio.
Anyway, they sang it for Denver, who recalled, "I flipped."
The three of them stayed up until 6 a.m., changing words and moving lines around. When they finished, Denver announced that the song had to go on his next album.
The three of them debuted the song at the Cellar Door in Georgetown, Washington, D.C. on December 30, 1970.
Released in the spring of 1971, the new song broke slowly, moving up the charts very deliberately. RCA called Denver after a couple weeks and told him they were giving up on the single. He told them, absolutely not.
Bill and Taffy toured with Denver and sang on his albums in the early 70s. In 1974, they added a singer named Margot Chapman and a teenaged piano player/vocalist named Jon Carroll and formed the Starland Vocal Band.
Yep - "Afternoon Delight", a monster #1 hit in 1976, was a product of the very same collaboration of Bill and Taffy that launched Denver into superstardom.