The 4-year-old daughter of Peintre Celebre ran the 1 ½ miles on the soft turf course in 2:38.77 and gave jockey John Jacinto his second stakes win of the meeting. He rode Dawn of War to victory in the Lane's End Breeders' Futurity (gr. I) earlier this year.
"My filly was very sharp and wanted to go all the way," said Jacinto, who is riding regulary at Keeneland for the first time. "I just tried to get her on the best part of the course.
"Thankfully, she relaxed for me. At the half-mile pole I had plenty of horse left and she really wanted to take off. When I let her go, she flew."
Cape Town Lass was second, 1¼ lengths behind the winner and two lengths in front of third-place Louve Royale. Jockey Gary Stevens was bidding for his 5,000th career win aboard Louve Royale, the 2-1 favorite.
"She's a filly that wants to run off," Stevens said. "I think she settled well today but when I came with my run, the top two fillies were just too much."
The English-bred Briviesca, who is owned by Darpat S.L. Stables and is trained by Bill Mott, improved her record to 16-5-4-0 and increased her earnings to $253,555 with the winner's purse of $93,000.
The winner paid $8.80, $5 and $3.60 as the third choice in the field of eight fillies and mares. Cape Town Lass, ridden by Rafael Bejarano, returned $4.40 and $2.80 and Louve Royale paid $2.80.
Strike Me Lucky finished fourth followed, in order, by October Glory, Beau Happy, Jordyn Macoma and Sheer Luck.