She had earlier in the journey recorded herself on her phone while swerving on the gravel edge of the road. 

Tientjes crossed onto the wrong side of the highway and collided with a car driven by Rishab Jaiswal, who tried to take evasive action.

Mr Jaiswal's wife Shadari Athrey was thrown from the car and died at the scene. 

The pair, who had been married for just over a year, had travelled from Queensland and arrived in Tasmania the day prior. 

"The impact on Mr Jaiswal has been devastating," crown prosecutor Mick Allen told the Supreme Court of Tasmania on Wednesday.

Tientjes, who was in the car with her friend and their young child, suffered a minor injury to her right thumb. The child was not injured. 

Mr Allen said Tientjes' culpability was extremely high as she knew she had not slept, was extremely tired and had consumed drugs immediately before driving.

"There is clear evidence she had been driving recklessly in an early part of the same journey," he said. 

"It is not an isolated act of driving. All road users in that area were exposed to the risk." 

Tientjes and her friend had spent the night before the crash on a boat moored at a nearby jetty with a fisherman. 

A man who saw her drive away on the morning of Good Friday told police "her eyes were glazed like she was off her head". 

Tientjes, who has prior driving convictions, also pleaded guilty on Wednesday to a host of other charges relating to the crash. 

She admitted having illegal drugs, including methylamphetamine in her system while driving, reckless driving, and possessing a bong and glass pipe. 

She also pleaded guilty to smoking inside a car while a child is present, driving without a licence, altering a number plate and using an unregistered car. 

Her sentencing hearing is expected to resume on June 20.