She was seen drinking from a bottle of wine while driving at speeds well in excess of the legal limit, according to a summary of facts read to the court.
She mounted the kerb at times, crossed the centre-line and ploughed into a bank during the 4.3km journey.
After her heavily damaged Mercedes-Benz came to a stop, McWilliams got out of the vehicle and fled on foot for a further 300m before members of the public who had been following the car detained her until police arrived.
She refused to provide a breath-alcohol sample or blood to police, but arresting officers said she was "smelling strongly of alcohol'', the summary said.
She was only a restricted drivers licence at the time of the incident and its warrant of fitness and registration were expired.
The other two charges were related to an incident in June.
She was charged with assaulting a police officer, resisting the same officer and disorderly behaviour.
She pleaded not guilty to those charges earlier this month, but following the withdrawal of the disorderly behaviour charge by police yesterday she pleaded guilty to the assault and resisting arrest charges.
The charges stemmed from a drunken argument with her sister on June 6.
The pair were arguing in a car when McWilliams, who was intoxicated, forced her sister out of the car and was found by police in its driver's seat when they arrived.
Upon arrest, she punched and kicked a steel divider in the processing area at the police station and twice kicked the arresting officer.
She couldn't be spoken to by police about the matters "because of her drunken state'', the summary said.
Judge Phillips remanded McWilliams on bail for sentencing on November 10.
He called for a full alcohol and drug assessment of McWilliams ahead of her sentencing.
