To improve the prompt for generating an AI image, I would suggest removing the reference to the girl's age, as AI images are not capable of accurately depicting age. Instead, focus on providing more detail about her surroundings, such as the texture of her dress and the specific type of lavender flowers in the field. Additionally, you could include details about her facial features, such as the shape of her nose and the curve of her lips, to make the image more distinctive and memorable.