I don't think it will happen. Horses have excellent memory - I've seen them recognize past herdmates they see several years after parting, they also remember fantastically acurate details from training even if left as pasture puffs for a very long time, or, let's say, characterstics of their abusers, e.g. become afraid from men with black cowboy hats for life, if such a man has abused them when they were still foals.
She might get friendly with her new owner, but she will most likely remember you. When Snickers was a lesson horse he was taken for a month to a summer camp where he worked as a guided trail ride mount, but, when he returned, he still nickered first thing as he saw me coming. These things don't fade that easily.
I have come a long way, to surrender my shadow to the shadow of my horse.