The four-year-old filly, owned by Anthony Oppenheimer, is likely to be retired after the Group One feature, while Vaughan announced in July he is relinquishing his licence after 16 years.
Dame Malliot – who is set to be ridden by Hollie Doyle – has given Vaughan a pair of Group Two victories and has finished third at the top level twice this term.
Her latest run, when third in the Prix Vermeille after setting the pace, has worked out well – with the winner, Tarnawa, and the placed horses, Raabihah and Wonderful Tonight, boosting the form on Arc weekend.
“We were pleased to see the Vermeille form working out extremely well,” said Vaughan. “David Menuisier’s filly (Wonderful Tonight) won the Prix Royallieu, which we were going to run in but we just decided we’d give her a little more time and wait for this one.
“I was pleased with her run in the Vermeille. She only got chinned on the line for second place, beaten a head by Raabihah who ran a great race in the Arc.
“I suppose when you’re making the running you’re always there to be shot at and it’s hard to make all, but she lost nothing in defeat.
“Hollie will ride her at the weekend, all being well.”
Vaughan reflected on Dame Malliot’s career, during which she has only run eight times but has been successful on four occasions.
“She’s been a wonderful servant. She started off at Wolverhampton in a median auction maiden and is running in a Group One in what looks like her last start,” the Newmarket handler told Sky Sports Racing.
“It’s been wonderful to be associated with a nice filly like her. As for her future, I don’t know. It’s up to the owner. I think it’s more likely she’ll be retired, I imagine.
“She’s done incredibly well. I’m sure the owner will want to start breeding from her next season.
“I’ve nothing nailed down yet. It doesn’t look I’ll be staying in England. I’ve a few things in the pipeline. I’ll take a bit of time off at the end of the month and go from there.”
Select any odd to add a bet