It was a battle of the veterans in the final, with Twigg beating fellow 39-year-old Erin James by nine seconds.
James, who rowed with Twigg at the 2003 Junior World Champs, returned to the sport last year after a 17-year break.
Twigg, meanwhile, appears set to pursue selection for the next Olympics.
“We’ve got qualification next year, there’ll be a continental qualifier and then world champs will be a qualifier as well. Then we start looking at what’s going to happen in terms of prioritising boats for selection as we head into an LA format … It’s going to get spicy.”
Cambridge’s Matt Dunham won the men’s open single against Waikato’s Seb Fulton and was feeling it afterwards.
“I had to race my guts out to go toe-to-toe with Seb. Man, the whole field’s just getting better and better.”
Dunham is also hoping to win selection for worlds and eventually make the team for Los Angeles.
He and James rowed the mixed double in Turkey last year, where they finished inside the top 16.
Twigg and Michael Brake beat James and Dunham in the final of Mixed Open Double.
“I love that I can just push as hard as I bloody can and give Matt and Erin a challenge … as long as I can hold my own and Twigg does her thing like the legend she is, that raises the standard for our whole team,” Brake said.