A police spokesperson said while the initial investigation into the crash had been completed, the Serious Crash Unit was yet to determine a cause.
"The file has been referred to the Coroner, as are all files of victims who pass away in these circumstances," the spokesperson said.
Aside from simply wanting closure, Frow said the family has had difficulty accessing life insurance and her mother's estate.
"The funeral will be paid for but we've just got to wait and do this process first," she said.
Frow said the family could not access life insurance until there was an official cause of death, and have to go through the courts to settle her estate as she had no will.
The family has also set up a Givealittle page to raise money for the funeral.
The family had been told by police that speed was not a factor and drugs and alcohol were not involved in the crash.
There was another fatal crash just north of Kaitaia, and a crash causing serious injury on the Paihia waterfront the same day.
"Dad rang the Coroner the other day and they've still got nothing for us. They just said it could be several months before they can come up with something," Frow said.
There have been long delays for coroner's findings to be released in recent years, with the average time to close a coronial case rising from 321 days in 2018 to 455 days in 2021.
Waits could be much longer in some cases. In 2021, cases needing an inquiry took an average of 877 days, and those going to an inquest took 1451 days.
The Government has announced funding for four new Coroners, seven coronial registrar roles and four clinical advisor roles to ease workload pressures.
Minister for Courts Aupito William Sio said the new funding of $28.5 million over four years and $1.6 million of capital funding was to ensure families received a coroner's findings sooner.
"The coronial process, by its very nature, can take time. It is designed to find out the facts about a death, provide resolution for families and produce findings that may help prevent future deaths," Sio said.
"However, undue delay can add to the grief and stress for families of loved ones who have passed. I know the coronial system is under pressure and that is why we have introduced these measures."
Anyone who wants to contribute to the Givealittle for MacArthur's funeral expenses can do so at https://givealittle.co.nz/cause/help-us-put-our-mumnana-to-rest
Coronial Services has been approached for comment on their processes and support for families, but did not respond by publication time.
Deaths that are reported to the coroner
• unnatural/violent deaths (including car crashes and drownings) and suicides
• deaths where the cause is unknown
• the person died in prison, police custody or care such as a mental health institution or residence run by Oranga Tamariki
• the person died unexpectedly during surgery or medical treatment
• a woman dies in childbirth or as a result of pregnancy
• the doctor hasn't issued a cause of death certificate
What happens when a death is referred to the coroner
• the coroner decides whether to ask a pathologist to do a post-mortem examination
• the coroner decides whether to have an inquiry and/or an inquest (a hearing held in court)
It can take several weeks for the coroner to decide whether to have an inquiry, and these can be put on hold if another agency is investigating the death.
