Three women pressured into having sex with an RAAF instructor in NSW when they were cadets say nothing has changed since a 15-year-old took her own life in 2000.

Eleanore Tibble killed herself when she thought she faced dishonourable discharge from the Australian Air Force Cadets in Tasmania for "fraternising" with a senior instructor.

Her distraught mother Susan Campbell told a royal commission on Monday her daughter died two weeks after senior air force officers decided she had no case to answer but the local command never told the girl or her family.

The sex abuse royal commission on Monday heard evidence on how the ADF and ADF Cadets handle allegations of child sexual abuse.

After Ms Campbell's evidence, three other witnesses told how in 2012 they were pressured into having sex with NSW cadet instructor Christopher Adams, who is now in jail for having sex with teenagers in his care.

Adams, 25, was jailed for two years last December with a 14-month non-parole period.

In emotional evidence on Monday, Ms Campbell said Eleanore was threatened with discharge because officers in her unit suspected she had an affair with an instructor.

The instructor had become obsessed with her but Eleanor did not become involved sexually.

The instructor resigned citing "fraternisation with a cadet" and Eleanore was told she needed to resign or be discharged.

She took her own life probably afraid she would bring dishonour on the family if she was dishonourably discharged, her mother said.

It was only after her death that Ms Campbell discovered Air Force Cadets officers in Canberra had investigated and decided her daughter had no case to answer and she should be reinstated.

Officers in Tasmania failed to inform her.

She buried Eleanore in her cadets uniform and fought to find out how it had happened.

"Someone sat on that order for over two weeks and, in this time, Eleanore committed suicide. I wouldn't believe it," she said.

On Monday, the women groomed by Christopher Adams all said nothing has changed 16 years after Ms Tibble's death.

One woman given the pseudonym CJJ said: "AAFC have held that things had changed since the Ellie Tibble case but the response of the AAFC and the ADF was still really poor" in response to Christopher Adams' behaviour.

"I would like the AAFC to recognise where they have gone wrong and through their actions they have hurt and traumatised people," she said.

All women told how from the age of 15 Adams targeted them, flirting, sending sexy text messages and befriending them on Facebook.

One witness CJI told how petrified she was when he got her alone in his room and had sex with her.

The commission continues on Tuesday when AAFC personnel will give evidence.