Millisle got off the mark for the season with a dominant success in the Yeomanstown Stud Ballyogan Stakes at Naas.
A Group One winner last year for Jessica Harrington in the Cheveley Park Stakes, the daughter of Starspangledbanner ran first time out this year in the 1000 Guineas at Newmarket before returning to sprinting at Royal Ascot in the Commonwealth Cup.
Her third run of the campaign was a runner-up finish to Art Power over this course and distance and she was sent off at 9-4 for her latest assignment.
Favourite Forever In Dreams jumped out in front, but Millisle and Shane Foley were quickly in attendance and headed the market leader inside the three-furlong marker.
She soon went clear, finishing a ready four lengths clear of Pronouncement at the line.
Harrington said: “She’s back on track. She was very good there and Shane said she’s only really learning to sprint now.
“She got rolling, enjoyed it and quickened up well. She had to carry a penalty against them there, too. We’ll probably go to the Curragh now for the Phoenix Sprint, another Group Three.
“It’s just hard enough to find races for her. There are very few fillies races, that’s the trouble, and she’s probably not hardened enough to take on the elder sprinters yet.
“I think she will be in time as I think she’s a proper sprinter. I’d love to look at a Group One towards the end of the season.
“She seems to go on any ground, it doesn’t seem to worry her at all.”
She added: “She’s won a Group One, a Listed race and now a Group Three, so it’s brilliant. She’s a very valuable filly as she has a good pedigree, too.
“Her dam went back in foal this year to Starspangledbanner aged 23. She had been retired, but they brought her back in out of the field.”