Multiphotograph Nick DeWolf took pictures in 1978 from a Jam of Bluegrass Musicians in Aspen, Colorado. Among them a bass playing woman, wearing blue jeans, red sweater and a denim vest.
https://www.flickr.com/photos/dboo/
She also appeared at an inhouse gig:
Another show, another crowd and two more women with denim vests. One appeared only one time for sure on the picture, the other one can be longer tracked.
Brotherhood of Man is an iconic British music group from the 1970s. Famous for winning the Eurovision Song Contest in 1976. There is a set of band photos showing Brotherhood of Man in unique denim outfits with both women (Nicky Stevens and Sandra Stevens) wearing denim waistcoats. Pictures found in the WWW
Brotherhood of Man also wore the denim outfits while some 1975 TV performances:
Swedish singers NOVA and the background choir THE DOLLS performed 1973 for Sweden at the Eurovision Song Contest. I'm not sure about the outfits of the three dolls. Maybe there are early denim vests, definitely the outfits are vest inspired.
