they do exist. didn't the protagonist use colored contacts in the beginning because she was told to hide her real eyes?
As you have seen from a couple of chapter before when nera was reading through the book about plastic surgery, she found a page about eye surgery and only a magican or someone who knows about their first life can perform it. Nera stated that they had someone like iris and so she probably when to them do they can perform eye surgery, to change her eyes. As for how they can believe her , she went to the maid to get the letter of iris mother stating that iris is her daughter , but changed the letter from iris to her name , so to make it look like that she's their daughter through the writing of iris mother. Hope that makes sense.
I'm so confused, color contacts don't exist in this world and Nera obviously had green eyes before, plus she has bright pink hair which neither Duke nor duchess have, so how tf do they think shes their daughter(╯°Д °)╯╧╧