there was a mare Just One More Time xx who was sent to the Netherlands and used for KWPN breeding. Not sure if that's what you mean by "international broodmare".
Just to update
1974 ONE MORE TIME IV was grade A drk bay mare standing 1.62 her BSJA nbr 82727
1969 ONE MORE TIME II was grade C bay mare standing 1.62 her BJSA nbr 54590
I would think the horse you are looking for therefore is the 1974 ONE MORE TIME, is this horse too old?
Could it be Lesley McNaught's mare? Bay with a white face, another suspected Irish-bred of unknown breeding. Lesley (now McNaught-Mändli) won an individual gold medal at the 1981 European young rider championships with her around the time she was based with the Edgars. Think she and her team-mates, Mark Heffer was one, won team gold as well?