"In a flash, in a moment, I saw the dark side of a man who I thought could be trusted," the woman said before being overcome with emotion.
"He slid his hand down my back against my bottom and then in a moment put his hand up my skirt and tried to put his hand in between my legs."
She told her mother within days that Harris was a "disgusting, vile and repulsive man" who'd destroyed her trust.
Years later she told her husband and in 2013 after it was reported Harris had been arrested she contacted British police.
Defence lawyer Sonia Woodley QC suggested Harris' hand may have "innocently" wandered down her back.
During a heated exchange the witness snapped: "How do you sleep at night?"
The court further heard from a woman who said Harris pushed her against a wall and slobbered over her when she was holidaying in Malta in 1970.
The then 18-year-old had been discussing one of the artist's paintings hanging in a bar when he allegedly said: "I've got some more if you'd like to see them?"
The teenager followed Harris into a side room where he started kissing her in a "slobberly" way.
He allegedly touched her breasts before putting his hand inside her underpants. Afterwards she was relieved.
"I was happy that was it," the witness explained to the jury.
"I thought I was going to be raped."
Ms Woodley suggested Harris never touched her but the woman insisted: "I can assure you he did."
The court also heard how Rolf Harris "tongue kissed" an Australian girl aged 11 or 12 immediately after asking her how old she was.
The assault allegedly occurred in Darwin in 1969 when the girl was dressed only in her pyjamas.
The alleged victim, now in her mid-50s, was off school sick at the time and staying with family friends. Harris was also a guest.
The girl went downstairs to an area under the house where Harris was working with wood, the entertainer's indecent assault trial heard on Monday.
He allegedly asked her how old she was and, after being told, said: "Good I want to be the first one to introduce you to a tongue kiss."
The girl froze and the "very tall" Harris rubbed his hands up her sides and enveloped her in a hug, the witness told Southwark Crown Court.
"He put his tongue in my mouth and gave me a tongue kiss," she said.
"It seemed like it lasted forever but it must have been quite quick.
"I was ... absolutely repulsed."
The alleged victim subsequently told girlfriends that "my first tongue kiss was with Rolf Harris" but no one believed her.
Later in life, the Australian woman told her husband when explaining why she had an aversion to people approaching her for a kiss.
"It makes me feel very frazzled and scared - I almost have a panic attack," the witness said.
The three women who gave evidence overnight NZ time are supporting witnesses for the prosecution.
The entertainer can't be charged over the incidents because they occurred outside the UK before 1997. The law has subsequently been changed.
The trial continues.
