Mabee died at her Rancho Santa Fe, Calif., home after an extended illness, her only child, Larry, announced.
Between 1990 and 2001, the Mabees were consistently named California's leading breeders. In the 1990s, they won three Eclipse Awards as the outstanding Thoroughbred breeders in North America.
The Mabees were a true team, said Joe Harper, president of the Del Mar Thoroughbred Club.
"For many years, they had the most successful breeding operation in the state. They also were both instrumental in Del Mar racetrack being . . . one of the most successful tracks in the country," he said.
After her husband died at 80 in 2002, Mabee and her son continued to run Golden Eagle Farm, a 568-acre spread that the family established in 1972.
She also moved into the Del Mar boardroom in 2002, becoming only the second woman in the track's history to hold such a post.
Her favorite racehorse was Best Pal, who was bred at her farm and won more than $5.6 million, including the inaugural running of the $1-million Pacific Classic at Del Mar in 1991.
Born in Unionville, Mo., in 1921, Mabee grew up on an Iowa farm, as did her future husband. High school sweethearts, they married in 1941.
After moving to San Diego in 1943, the couple invested $2,000 in a mom-and-pop grocery store that grew into the Big Bear supermarket chain. They sold it in the early 1990s.
"When you have a store about the size of a family room, and there are only two people, you are it," Mabee told the San Diego Union-Tribune in 1991. "All of our farm training didn't hurt. . . . We were used to working from dawn until dark."
From 1984 to 1997, the Mabees owned Golden Eagle Insurance Co., employing more than 1,300.
Dedicated to community projects, she started a secondhand thrift shop in Chula Vista to support San Diego's Aseltine School for children with learning disabilities. She also founded a number of auxiliaries and volunteered widely.
In 1957, her interest in racing had been sparked by the purchase of two yearling Thoroughbreds, the Coal Baron and War Missile.
Racing "has been such a wonderful world," Mabee said in 2002. "I couldn't imagine being without it."
In addition to her son, she is survived by three grandchildren.