Is this the normal height for a 10 year old?

My litter sister is 10 years old and is turing 11 next month. She is 5'4 and is the tallest in her cl, is this abnormal? Or is it just because she likes to take vitamins every day? Please answer this question, I'm a bit worried and yes the docter has already seen her but has made no comment or has offered any advice.