The title came in only her fourth show back after having her baby.
"I'm still getting my eye back in and to be honest in the first round he went to stop at the first jump and I had to growl at him and ride him really aggressively," she said.
She managed to record a clear round and then improved on that performance in the jump off.
"I had an advantage because I was last and knew I only had to go clear to win but I didn't want to go slowly in case he pulled a rail, but he didn't touch a thing so I was really happy with him in that round," she said.
Gravatt didn't push her luck at the two-day two star event, shying away from the Horse Grand Prix on Sunday and she plans to stick around the Pro-Am height until Christmas at least.
"I'm not planning to do any Grand Prix until I get a bit stronger, I've lost a lot of muscle and strength because I didn't ride at all when I was pregnant," she said.
Auckland's Douglas Thomson finished second on Marksman Arrow, with Pukekohe's Sarah Beal third riding Ynot.
Another Northlander Amanda Wilson won one of the other main two star events decided on Saturday with a win in the Young Rider Class.
Wilson dominated the class, with jumps ranging in height from 1.30-1.40m, by riding Showtym Viking to victory and Showtym Cassanova into third place, with Pukekohe's Rebecca Van Tiel taking second on Adeaze.
The Junior Rider Class was won by Auckland's Laura Inkster, with Hester Gerrand second and Northland's Nakeysha Lammers third.
Lammers improved her performance on Sunday by winning the well contested Pony Grand Prix. With no riders going clear in the opening round, 10 riders with four faults had second chances and contested the jump off.
Lammers, riding Airborne Magic, beat off the challenge of her sister Sharnaye on Watch Me Move with Bryony Smith riding Homeland Hero in third. Kieron Cooper and Ella Poole-Crowe finished in fourth and fifth respectively.