Gin Dartre won the listed $75,000 South Island Breeders' Stakes (1600m) at Riccarton on Saturday after racing three wide back in the field.
It was her first win over 1600m but Thornton said he had always considered the daughter of Volksraad and staying mare Rapida would master the distance.
The options for Gin Dartre are to remain at Riccarton for the listed Great Easter Handicap (1400m) there on April 4 or return home for the group one $200,000 New Zealand Thoroughbred Breeders' Stakes (wfa, 1600m) at Te Aroha the same day.
"We'll assess the likely field at Te Aroha before making a final decision," Thornton said.
Gin Dartre had recorded placings in her two previous visits south for listed races and registered her first black type win with Lisa Allpress in the saddle.
Gin Dartre won her previous start at Matamata and Thornton said the addition of blinkers that day had been a help.
Her name is an amalgam of her owners' first names - United States businesswoman Virginia Parker, Sydney-based New Zealander Darryl Courtney-O'Connor and Sydney businessman Trevor Loewensohn.
Courtney-O'Connor bought Rapida out of the Sydney stable of Gai Waterhouse and had success with her first foal, Courtney.
• Eel Win, who mastered 59.5kg to win the Hororata Cup at Riccarton on Saturday, will be nominated today for the Riverton Cup.
Eel Win, owned by Sabin and Clare Kirkland, of Invercargill, is trained at Yaldhurst by Michael Pitman, who won the Riverton Cup last year with Borninthestates.
Pitman won the Hororata Cup in 1994 with Noble Task and 2007 (Coup Christchurch).
It was the 14th win for Eel Win in 42 starts and took his stake earnings to $288,575.
David Walsh, who rode Eel Win, won the Hororata Cup last year on Le Alto.
The $100,000 Riverton Cup (2147m) is on April 11.
Jillian Morris was suspended for careless riding at Riccarton on Saturday.
Morris, the rider of Bent in the South Island Breeders' Stakes, was found to have shifted ground at the 1500m, causing a check to Monkey Magic.
She was suspended until April 5 inclusive.
