Amanda is likely around 9 to 12 years old. This estimation is based on contextual clues such as her being a school-going girl, being scolded by her mother for typical behavior of that age, and references to stories like "The Mermaid" or "Rapunzel" that are commonly read by children in that age group. Additional clues include her innocence and immaturity as described in the context of a poem or story referencing Amanda, where the parental instructions and Amanda's imaginative nature fit this age range.

This age estimate is derived from interpreting contextual indicators rather than explicit information about Amanda's age, as there is no direct statement of her age in the references found.