Samantha Thomas, 38, of Meredith, narrowly avoided jail and was convicted and fined $2500 after pleading guilty at the Ballarat Magistrates' Court on Monday to careless driving, drug-driving and unlicensed driving. 

Magistrate Ronald Saines said Thomas had a "gross and serious misjudgment of whether you should have been in control of a vehicle.

"You are a serious danger to yourself and others."

The court heard Thomas had taken a cocktail of heroin and ice only four days before the three car collision which partially blocked the Midland Highway, near the Finns Road intersection at Scotsburn, on June 8.

Police prosecutor Sergeant Ivan Blomley said another driver saw Thomas, who was travelling north-bound, drift from her lane close to other cars and the guard rail before crossing the double lines onto the other side of the road.

Thomas then hit a ute hard enough to send it into the air, landing on top of the guard rail. 

Both the driver and his male passenger were uninjured.

Thomas, who did not break or slow down, then crashed into a Nissan Patrol, leaving the elderly female driver with minor injuries.

The court heard Thomas' learners permit had expired earlier that year, she had drugs in her system and was fatigued when the crash occurred. 

Her lawyer, Manny Brennan, told the court his client was shocked and incredibly remorseful for her actions.

He said Thomas on the day decided to get behind the wheel because her daughter missed the school bus and needed another way of getting to school.

Mr Brennan added the weekend of drug taking was not reflective of his client's general behaviour, saying it was simply a slip-up.

He said she had since sought treatment to ensure it wouldn't happen again.

With no criminal priors for driving related matters, Mr Brennan urged the magistrate not to convict his client.

Magistrate Saines rejected the submission.

"Are you serious?" he asked Mr Brennan.

"It's one of the busiest highways in Victoria ... there could have been a double fatality.

"What the court should be considering is whether a term of imprisonment is in range."

While two of the charges Thomas faced were not punishable by jail, the unlicensed driving was for a first time offence.

Mr Saines told Thomas her efforts to address any drug problem she had, and her lack of criminal priors saved her from imprisonment on Monday.

He told Thomas the fine was intended to hurt, but added she would likely be sentenced to a long term of imprisonment if she returned to court on similar matters in the future.

Thomas was also disqualified from driving for a year.