Charlotte, who gave evidence under a pseudonym to an inquiry into child sexual abuse in public institutions, said a worker "Edwin" left her alone with four boys who "did what they wanted" with her.
She was on an off-site trip with a worker who left her alone with six boys. She said one of the boys had sex with her in a hut.
Charlotte was in Ashley several times from the age of 12. She told the inquiry Edwin was "sleazy", touched her legs while they played cards and said he wished she was older.
Edwin wrote "bite me" on the chest of her friend, a fellow detainee. Charlotte said workers saw Edwin do it, and nothing came out of her complaint.
She started self-harming when she was locked in her unit.
"This lady worker came in .... she slammed my head into ... a wood bed base sort of thing and told me to 'grow up and stop doing it, that's making more paperwork'," she said.
"After that I just felt like I couldn't say anything otherwise I'd get it off the workers as well."
The state government has recently reiterated its pledge to close the centre, which has operated for more than two decades, by 2024.
National Children's Commissioner Anne Hollands on Wednesday joined calls for the facility to be shut immediately.
Charlotte says she lit her unit on fire because she was nervous about an impending strip search that required her to be fully naked in front of two people.
She was left in her unit for days without a change of clothes.
Despite Ashley having a school on site, Charlotte said she didn't receive an education there and doesn't know how to read or write.
"I was pushed into a room and nothing really. I have no words," she said.
The centre has been described as having a culture of dehumanisation and brutality, with former detainees saying they were raped and bashed by guards and told not to speak up.
"I can't be around any bloke. I just don't like anyone touching me at all," Charlotte said.
The centre's manager on Tuesday told the inquiry it was a failing he didn't "pick up" on an email from a staff member about the alleged sexual assault of a detainee.
Stuart Watson, who took up the top job in February 2021 after about a year as assistant manager, was pointed to an email in which a clinical practice consultant raised concerns.
"The only thing that I can suggest is that that email went to a couple of other people and perhaps at the time I thought they were managing it," he said.
"I don't know, I can't recall. But I am extremely concerned and troubled by the fact I didn't pick up on it and I can recognise that as a failing."
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