There are two Group Ones remaining in Europe in which the five-furlong specialist could participate - the Flying Five at the Curragh and the Prix de l'Abbaye at Longchamp.
Winter Power's progression has been remarkable since her first win, which came in a Redcar nursery off a mark of 76 last July.
She ended her juvenile campaign with victory in the Cornwallis Stakes, but she still appeared to have plenty of ground to make up on the best sprinters.
Two victories at York sandwiched a creditable performance in the King's Stand at Royal Ascot before her success in the Nunthorpe.
"She's come out of the Nunthorpe well and she's in good form," said Easterby.
"We don't quite know what the plans are for the rest of the season yet.
"There are two obvious races, the one in Ireland (Flying Five) and the (Prix de) l'Abbaye, but she's just nicely back from the Nunthorpe so we've no idea yet.
"She could run in one or both, I don't know yet."