Mayorkas posted a final-round, 2-under 68 to join Dennison, who fired a 65 on Sunday, in a tie at 11-under-par 199.
Mayorkas, a three-time All-American at UCLA, birdied her final hole in regulation to force the extra session. She collected $10,500 for her first win as Mayorkas collected four top-sixes this season.
In-Bee Park (68) and Angela Park (67) shared third place at 9-under-par 201.
Erin Kerr (67), Randi Meadows (66) and Lee-Ann Pearce (65) tied for fifth at minus-8.
Allison Fouch and Meaghan Francella both posted rounds of 3-under 67 on Sunday to tie for eighth at minus-7. Kristy McPherson (73), Kristen Samp (71) and Kellee Booth (66) finished one shot further back at 6-under-par 204.