Sherri Turner finished third with a 65 that set a course record.
She played little in the 1980s but remained a presence around the tour and sometimes caddied for 1988 LPGA Championship winner Sherri Turner.
Sherri Turner, winner of the L.P.G.A. Championship earlier this year, finished at 282 after a 72.
Rizzo and Sherri Turner played all five holes of a playoff that began with four players.
This championship was won by Sherri Turner.
"The Tour is wide open now," Sherri Turner, an L.P.G.A. player, said after her round yesterday.
Sherri Turner, was at 138 after a 71.
Sheehan, who led after Thursday's first round with a 68, had a three-day total of 9-under 207, one shot ahead of Sherri Turner.
Sherri Turner led the money list with earnings of $350,851.
Sherri Turner was another stroke back, and no one else was within six strokes of the lead.