The two were at the Sleepy Ridge golf course in Orem when Aria Hill was struck by a ball in the back of her neck while sitting in a golf cart, Orem police Lt. Trent Colledge said.
She was flown to a hospital in Salt Lake City in critical condition and died from her injuries hours later. The girl's uncle said Hill often went golfing with her father.
"She loved doing it and had a good time with it all," David Smith told the Deseret News. "That was one of their things that they would do together. It was something that was really important to them and something they did all the time."
Police were investigating the incident but it appeared to be an accident, Colledge said.
Orem is about 40 miles southeast of Salt Lake City.