After opening with a 6-under 67 to take a three-stroke lead, the 51-year-old Rinker had a 74 on Sunday to finish at 5-under 141 on Innisbrook Resort's Island Course. She earned $30,000.
"It's hard to play when your stomach is in your throat," said Rinker, a two-time winner on the LPGA Tour. "I actually started out good on the front and was doing really well, but a couple holes before the turn I started choking up a little bit. I hit two poor shots that I can say were because I was nervous."
Mucha had a 69, and Johnson and Kane shot 72.