The drop back to the minimum trip did the trick for Sun Queen as she got off the mark under Seamus Heffernan.
The 11/10 favourite tracked Marvada throughout before joining that rival at the two-furlong pole.
The Aidan O'Brien-trained daughter of Storm Cat soon edged ahead as Balmont Mast also threw down a challenge to make it a three-way battle.
Sun Queen always had too much in hand for her rivals, however, and kept on strongly inside the final furlong to record a half-length victory over Marvada. Balmont Mast was the same distance back in third.
The winner had been placed over seven furlongs on her two previous starts but showed plenty of pace back at five today.
"She's a genuine fast filly but is still a little bit weak," said Heffernan afterwards.
"I was confident she would win but didn't want to give her any harder race than I had to. Hopefully she'll win again."
