Having turned down some "obscene offers" from predictable would-be buyers over the winter, the dream now moves on to next month's Stan James 1000 Guineas after a success achieved despite the winner taking a diagonal route from the two-furlong pole to the finish.
The 9-1 chance, returning to the scene of her Rockfel Stakes triumph of last season, was quickly away and soon in pole position under Michael Fenton in the Group Three contest.
Even when Speciosa started to veer left across the track, Fenton refused to be alarmed and performed a delicate balancing act of pushing forward while sitting slightly to the right in the saddle, enabling the winner to keep going all the way to the line.
And although the manoeuvre cost ground which saw the pack close up on her in the final stages, she had enough in hand to defeat Spinning Queen by a length, with Salut d'Amour a further three-quarters of a length back in third.
Owned jointly by Sly, her son Michael and London GP Tom Davies, it was no surprise that her fine end-of-season two-year-old form saw the daughter of Danehill Dancer attract attention from potential purchasers.
"They were obscene offers and I told them to take the money," said the trainer, who bought Speciosa at the Doncaster Breeze-Up sales for 30,000 guineas. "I said 'You're wrong, you're wrong.' But they were right. They said that they wanted to live the dream with her."
Sly, who describes herself as 'a farmer from the Fens' and trains a team of mostly jumpers just north of Peterborough, is now hoping for a draw against the left-hand rail in the Guineas in order to help steer Speciosa in the right direction.
"I'm going to have to ring Michael Prosser (clerk of the course at Newmarket) and make sure we get drawn in stall one, right on the stands' side," she smiled.
"I'm delighted because she is just not fit and I really think she will improve. I made sure I told the press that she was only 90% for today and I'm looking forward to Newmarket.
"I think we'll be coming back here for the Guineas rather than going to France as my French isn't very good. My Irish isn't much better but we might go there after Newmarket.
"She has veered left before but she will do that. She doesn't mind going across other horses as she likes to intimidate them.
"She was a very fraught filly last season but I think she has grown up. She was on a magnesium compound last year but she's medication-free now."
Fenton has done well on the handful of horses that Sly has campaigned on the Flat, most notably multiple handicap winner San Antonio.
And it is a partnership that will now yield a Classic ride for the jockey, who was thankful that offers to buy the filly were turned down.
"I begged them not to sell because I hoped that now we had got her right she could be a very good filly," he said.
"We'd have been happy to see her run halfway up the hill today because she definitely isn't fully fit.
"I had a feeling that she might start to hang on me but you can't fight her and once she met the rail she was picking up again."
Sponsors Stan James are best-priced about Speciosa's 1000 Guineas hopes, cutting her from 50-1 to 25-1, the same quote as VC Bet and Cashmans.