The average 15 year old girl stands at an average height of 4 feet and 11 inches tall.
So a 15 year old girl should be either close to 5 feet tall and some 15 year old girls can be 5 feet tall it just depends on the genes that are passed down to the girl from her parents.
I went to school with a 15 year old girl who stood 5 feet 5 inches tall while I was only 4 feet 11 inches tall myself so height can vary but on average 15 year old girls are nearly 5 feet tall.