Dermot Weld has confirmed Tarnawa will head to the Breeders' Cup meeting at Keeneland following her victory in the Prix de l'Opera at ParisLongchamp.
The four-year-old will have the choice of the Breeders' Cup Filly & Mare Turf or the Turf, where she would take on colts and geldings.
Weld admitted leaning more towards the Turf should the ground be firm as it is over her optimum distance of a mile and a half compared to the mile and a quarter of the Filly & Mare race.
"The present plan is Champions Day will come too soon because she has had a busy couple of months," Weld told Sky Sports Racing.
"She was a good winner at Group level here in Ireland in August and I just feel the extra time to the Breeders' Cup would be beneficial.
"No decision will be made yet whether it will be the Filly & Mare or the Breeders' Cup Turf.
"I would like to see nearer to the day. It will be early November and I've been in Kentucky when they've had snow at that time of year, so don't take it for definite the ground would be firm.
"Those factors will come into my mind.
"If it was fast ground, we might look more at the mile and a half (Turf).
"You must remember she's won three Group races over a mile and a half. She is very effective over that distance."
Weld reported Tarnawa to have taken the Opera in her stride.
"She came back immediately after the race yesterday evening," said the County Kildare trainer.
"She's in great shape and was out in the field this morning and was as happy as could be.
"She's a very good filly to win those two Group One races (Prix Vermeille and Opera), so competitive, back to back - (it) was a big achievement.
"We weren't sure she'd handle the ground with the speed she has, whether she would as effective on that surface, was my concern."
While Tarnawa may not be heading to British Champions Day at Ascot, Weld has yet to decide whether his dual Irish St Leger heroine Search For A Song goes for the Qipco British Champions Long Distance Cup.
"The decision will be made whether she goes to Ascot on Champions Day for the Long Distance Cup," he said.
"We'll look forward to training her next year and win another Irish St Leger with her.
"She's not the easiest lady in the world. Things just didn't go her way earlier in the year. She has had her moments. It was a matter of regaining her confidence and that's what we achieved."