The two-length victory was the third in as many starts for the Kentucky-bred, who notched scores at Saratoga and Monmouth, before heading north of the border.
The favoured daughter of Forest Wildcat quickened impressively inside the final furlong after early splits of :22.67 and :45.41, set by Real Fancy Runner. Second choice Holiday Girl rallied along the rail to finish second, while Hooh Why was third.
Jockey Emma-Jayne Wilson was pleased with the filly's effort.
"You couldn't have planned it any more perfectly," said Wilson. "Sitting on the outside, watching the inside speed, I was waiting to say go and she was already keen to go. Then when I said, 'Go,' she went."
Selva broke her maiden over a sloppy main strip at Saratoga by 1 ½ lengths in her career bow on August 7. The effort prompted her connections to run her in the six-furlong Sorority Stakes on August 31, which resulted in a half-length triumph.
Carroll believed the dark bay, who fell ill leading up to a September start at Presque Isle, would be at her best in the Glorious Song.
"She showed a lot of heart and guts in the Sorority and had to battle hard for the win," he said. "She had a couple of works on the Polytrack at Keeneland and indicated that she would handle the surface no problem.
"She's very professional. She was always in the race from the word go. She was just waiting for Emma's command and when she did, she went."
The two-year-old filly is owned by Helen Alexander and Helen Groves.
Selva paid $6.10, $3.40 and $2.90 across the board, combining with Holiday Girl ($4.60, $3.60) for a $20 exactor. Hooh Why ($4.90) capped a $145.90 triactor.