The 17-year-old girl, was caught by police speeding at 145km/h in a signposted 90km/h zone, along the Mitchell Highway at Wongarbon on December 28.

In Dubbo Local Court on Wednesday, the teenager pleaded guilty to a P1 driver exceeding the speed limit more than 45km/h, and told the court it was due to a "lack of judgement".

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"It's caused me great distress, embarrassment and regret," she told the court.

When magistrate Brian van Zuylen asked the teenager why she was speeding she told the court it was because she "was distracted".

"Are you aware you could have killed yourself, your passenger or someone else on the road?," Magistrate van Zuylen said.

Magistrate van Zuylen said it was an "appalling" speed and warned the road rules were in place for a reason.

"I've seen the catastrophes that happen when people like you, who've only been driving for a few months driving at most extraordinary speeds, the death and mayhem they can cause," he said.

"The road rules are there to keep valuable young people like you alive."

"There's certainly an argument that you're old enough to drive a car, you're old enough to accept all the penalties that come with it."

Magistrate van Zuylen said references demonstrated the teenager was a "very admirable young person", worked hard and had plans for the future.

The initial fine of $2520 was reduced to $300 due to her young age.

"Hopefully you've learned a harsh lesson out of all this," Magistrate van Zuylen said.