"I say she's unremarkable, yet here she is having pleaded guilty at a very early stage to an offence of breathtaking stupidity," Mark Rosalky said.

"She wasn't thinking on the day and it was a stupid decision."

Recorded during a "highly emotive" time, the video was not taken for any nefarious purpose nor was it shared with anyone, the court heard.

In the clip, Johnson is seen smiling and raising his two middle fingers at Savignano, according to court documents.

Magistrate Laurie Robertson imposed a $3500 fine and a 12-month community corrections order during which the 22-year-old has to be on good behaviour.

The sentence was discounted due to her early guilty plea.

The maximum penalties for the offence are a $22,500 fine and 12 months in prison.

The magistrate described Savignano's conduct as "absolutely not acceptable" and expressed concern about a prior criminal record that she said could not be described as "limited".

"I am very concerned to read your criminal record in circumstances that you’re 22 years of age. You’re at a crossroads now," Ms Robertson said.

Police found the recording on Savignano's phone while investigating charges relating to a car crash at Heckenberg, in Sydney's southwest, allegedly involving her boyfriend.

In September 2022, the SUV Johnson was allegedly driving smashed head-on into a car containing siblings Alina Kauffman, 24, and Ernesto Salazar, 15, killing them both.

Police allege he fled the scene after crashing the Mercedes-Benz AMG while travelling at nearly double the speed limit for the 50km/h zone.

Savignano and Johnson's 62-year-old father Kagadour Hanna Kokozian have been charged with concealing an indictable offence and hindering a police operation.

Police allege Johnson, his partner and father discussed a cover story and made false reports to investigators following the crash.

Two others, Cruz Pamoana Davis-Tuka, 21, and Laila Moukhallaletti, 21, have also been charged with helping to conceal the crime.