An Iranian refugee fatally set himself on fire on Nauru after his partner became frustrated with a conversation with United Nations representatives about their plight, an inquest has heard.

The woman, who cannot be named for legal reasons, has painted a bleak picture of their life after leaving Iran for Australia in June 2013 while giving evidence at an inquest into Omid Masoumali’s death.

After being intercepted on their way to Australia by boat, the couple were taken to Christmas Island, then an immigration detention centre on Nauru, she told the Brisbane coroner’s court on Monday.

Access to water, communications and medical services on Nauru were limited, she testified, and they ate only once a day because “the other meals weren’t edible”.

Hygiene was “the worst you can get” and their showers were capped at three minutes.

Their complaints were met with comments to “go back to your country”, she told the inquest.

“The mental health system they provided there was rubbish,” the woman said through an interpreter.

“If there was any sickness regarding the [hot] weather the only solution was water. It wasn’t a good situation at all, especially for the women and kids.”

After they were granted refugee status, they lived on Nauru but were provided with little information about their bid to get to Australia. “That was the worst part of it,” she said.

In April 2016, the woman said, she sat down with visiting UN officials and told them of her plight, but became “upset and frustrated” when she believed the organisation approved of their treatment by the Australian government. “More people had come to cause more misery and pain,” she said.

Masoumali became “angry” when he saw the woman was upset after the conversation. The couple went back to their demountable housing before he left a short time later. When she went to find him, she saw he was on fire, she said.

The 24-year-old, who his partner described as once optimistic, “incredibly strong” and “completely healthy”, had poured petrol onto his clothes and lit them in front of the UN officials.

“He was yelling and screaming, ‘I burn, I burn’, and he was waiting for treatment,” she said.

Masoumali was taken to hospital, where a doctor said he could not treat him. It would take more than 30 hours to get him to the Royal Brisbane and Women’s hospital for specialist burns treatment.

Placards are held outside the Brisbane court where the inquest into Omid Masoumali’s death is being held. Photograph: Dave Hunt/AAP

The coroner, Terry Ryan, is expected to investigate what could have been done to prevent the death, as well as the health and medical evacuation services provided.

But the inquest will not investigate Australia’s treatment of or its obligation to Masoumali as a refugee.

A vigil was held outside the court before the inquest.

“[His family] want to ensure this never happens again to any other family,” their lawyer, George Newhouse, told reporters.

“Every death in immigration detention and offshore should be etched in the minds of every Australian.”