Carmen Pua was in the back of her brother Kevin's car as it travelled along Progress Road in Richlands last Wednesday when a fight erupted between the pair about 10.30pm.
Mr Pua told7 News Queensland in an unexpected move,his sister jumped from the back of his car.
Police at the scene said it was travelling"at speed"when she jumped.
"We just had a brother and sister talk,I give her a bit of a lecture,she didn't want to listen no more,"Mr Pua said.
The teenager,from Durack,suffered critical head and chest injuries when she fell onto the roadway.
Paramedics rushed her to Princess Alexandra Hospital,where she clung to life for five days.
She passed away on Monday morning.
The siblings'71-year-old grandmother was also in the car when the incident occurred.
She was not injured.
Police have urged anyone who witnessed the incident to call contact them.
Investigations are continuing.