Siyarafina maintained her unbeaten record with a smooth victory in the Saxon Warrior Coolmore Prix Saint Alary at ParisLongchamp, with Sky Bet making her 3/1 for the Prix de Diane.
It has been a rapid rise through the ranks for the Alain de Royer-Dupre-trained filly, who did not make her debut until April.
She then won a conditions race later that month, but was ruled out of the French 1000 Guineas after not working to her trainer's satisfaction.
Given a different Group One aim and stepping up two furlongs in trip, Christophe Soumillon always looked to have things under control and was content to sit some way off the pace.
It was Simon Crisford's Imperial Charm who had taken the field along and Andrea Atzeni briefly looked to have slipped the field.
With Andre Fabre's Fount, another previously unbeaten filly, dropping away, Siyarafina moved up ominously alongside Imperial Charm.
Without resorting to the whip, Soumillon drove his mount to the front and she was not hard pressed to hold off Olendon by a length with Imperial Charm third.
Soumillon told Paris Turf: "She had been working better for a few days, but she is far from 100 per cent.
"However, winning her Group One after three outings, it's great - especially as she is not yet in the best of shape.
"She blows a lot like a mare who lacks a real preparation.
"It was just a prep race. She's run three times for three wins, which leaves great hopes."
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