Bethany Jayne Gilmore and her ex-husband Douglaas Stephan Withnell are on trial in the West Australian District Court charged with carnal knowledge of a girl and indecently dealing with a child.

The complainant, who cannot be named, testified on Monday via video link and wept as she recounted the details of her alleged abuse.

She said the first incident happened when she was five and involved Gilmore inappropriately touching her during a bath.

But she admitted she did not react at the time.

"I was scared ... I just froze," the complainant said.

During another incident when she was 12, the complainant said she was visiting the accused couple's home when Withnell exposed himself and told her to "wait 'til later".

Shortly after, the couple allegedly took the girl to a dark bedroom where Withnell raped her on a bed.

"If it hurts, squeeze my hand," Gilmore allegedly told the complainant.

Withnell is also accused of inappropriately touching the complainant during a separate incident when she was 12.

The court heard the pair had previously been convicted of sexually abusing two of the complainant's sisters.

But Withnell's defence counsel David Jones told the jury during his opening address that it did not mean Withnell committed any crimes against the complainant in this case.

"It did not happen," Mr Jones said.

"A person can have a false memory for a variety of different reasons."

Gilmore's defence counsel Ashley Watson also asked the jury to keep an open mind.

The trial continues.

Australian Associated Press