He sentenced the 43-year-old to a six-month suspended sentence.
Derrett previously pleaded guilty to a charge of failing to comply with a Covid-19 order – a charge which carries a maximum penalty of six months' imprisonment.
The defendant arrived from Brisbane on June 27 and returned a negative Covid-19 test three days later.
On July 4 – a week before she was due to leave - she absconded from Auckland's Pullman Hotel before being found a couple of blocks away less than two hours later in Anzac Ave.
Saunderson-Warner explained her client found "nature calms her when she's in a difficult situation".
The defendant, the court heard, had been homeless for six months while living in Australia and suffered an exacerbation in her anxiety and depression.
Derrett's family were "upset" about her circumstances and returned her to New Zealand so they could lend their support.
The defendant, who had a history of substance-abuse issues, was now being supported by mental-health services, Saunderson-Warner said.
Court documents revealed Derrett entered an outdoor courtyard of the hotel, designated as a smoking area, fenced by a five-foot brick wall and surrounded by a hedge.
She spent 20 minutes in the area and "displayed signs of emotional distress", yelling and talking to herself.
The defendant went back inside the hotel but was back outside again nine minutes later.
Derrett shouted at staff through a window, and while on-site staff sought assistance she clambered over the wall and bolted.
Judge Phillips said he was satisfied the escape was "entirely" down to Derrett's mental-health problems and the fact they were untreated.
The judge said he hoped it pushed officials to examine people in quarantine to avoid further incidents.