Is 120 pounds overweight for a 14 year old who is 5'4''?

There is no specific weight for a 14-year-old girl (or a person of any age). We would need to know more about your height and body composition in order to answer your question because weight is related to height and body composition rather than age. To see the distribution of weights and heights of children at various stages, please see the page link, further down this page, listed under Related Questions. Alternatively, please feel free to ask the question again and include more detail.