A man allegedly ran down his sister with his car after her cat urinated on his computer.
The 19-year-old woman suffered a fractured spine, a fractured leg and a collapsed lung and remains in a serious condition in hospital.
An argument erupted between the woman and her 20-year-old brother about 2.30pm (AEST) on Wednesday inside a house at Winmalee, in the Blue Mountains, west of Sydney.
The stoush allegedly began after her cat urinated on her brother's computer.
Police say he dragged his sister across the floor and threw her cat into the car. The woman was then struck by the car outside the home.
Police have charged the brother with common assault and negligent driving and granted him bail to appear at Penrith Local Court on May 15.
The cat wasn't injured, police said.