A 50-year-old woman was allegedly drunk and texting while driving when she crashed into a family of four in Sydney’s north-west on Sunday night, police say.

The crash left a four-year-old girl fighting for her life and her mother, father and aunt in hospital with serious injuries.

Police have charged a woman with drink-driving and using her mobile phone while driving after four pedestrians were injured in a collision in north-west Sydney.

Fairfax Media understands the driver, charged with multiple offences relating to the crash, is Lisa Mottram, the estranged wife of former Parramatta Eels chief Denis Fitzgerald.

It's alleged Ms Mottram's white SUV struck the family just before 9.30pm on Sunday, as they walked along Hezlett Road in Kellyville.

Emergency services were called, and the girl was taken to The Children’s Hospital at Westmead in a critical condition with life-threatening head and internal injuries.

Lisa Mottram has been charged over the crash. Supplied

A 55-year-old woman, the girl's aunt, sustained internal and spinal injuries and was taken to Westmead Hospital, where she remains in a stable condition.

The girl's father, 45, and mother, 44, were also taken to Westmead Hospital. The man was treated for non-life threatening injuries, while the woman remains in a serious condition with injuries to her face, arm and pelvis.

Inspector Kate Orr from Traffic and Highway Patrol Command's crash investigation unit said the family were on holiday from Hong Kong.

"We're in contact with the consulate to contact the relatives overseas," she said.

Ms Mottram was taken to Westmead Hospital for mandatory testing and was later released.

Inspector Orr said her blood-alcohol reading was 0.113, more than double the legal limit.

"No one should get behind the wheel with any alcohol to that extent," she said.

"I would suggest no alcohol. But on top of that to be using your mobile phone is extremely dangerous."

Ms Mottram was arrested and charged on Monday with several offences, including three counts of dangerous driving, one count of causing bodily harm by misconduct, mid-range drink driving, using a mobile phone and negligent driving.

Granted conditional bail, Ms Mottram will appear in Parramatta Local Court on October 10.