She's not the only one. Dozens of workers at the site were being dramatically underpaid, in what Martin De Rooy from Young Workers Hub said is a classic case of wage theft.
For some companies, he said ripping off workers is a deliberate business model and bosses either carefully avoid complying with legislation, or simply don't care.
"The ongoing, systematic underpayment of workers can be deliberate," De Rooy said.
"On a work site with a majority of young people who don't know their rights and don't feel empowered to speak up, it's easy for employers to exploit them.
"Young workers also aren't taught how to read a pay slip, how to check they're being paid correctly, how to check their super is being paid."
Siva initially didn't speak up out of fear of losing her job. But a visit by union representatives saw the issue blown open, and she's now slowly being paid back.
But the damage has been done. For years, she lived pay to pay and had to sacrifice to make ends meet.
"When my grandma died, I had to take out a loan to be able to travel for the funeral. She lives on the islands. Then I had to struggle pay it back."
Her story is one of many being presented to a Queensland Parliament committee inquiry into wage theft, which advocates say is startlingly common — particularly across the hospitality, retail and warehousing industries.
The inquiry has received dozens of submissions, including stories of a waste management worker underpaid by A$35,000 and a high school student employed on a "trial" at a motel but never compensated.
Queensland isn't the only state examining the issue, with Victoria pledging to introduce jail terms and much harsher fines for employers found to be doing the wrong thing.
"Whether you're a convenience store chain or a celebrity chef, if you deliberately and dishonestly underpay your workers, if you deny or deprive them of what is rightfully theirs, you will face jail," Victorian Premier Daniel Andrews said.
It follows high-profile stories of hospitality staff not being appropriately paid at the restaurant group run by celebrity chef TV identity George Calombaris.
Brisbane retail worker Kate, who didn't disclose her last name, believes her boss underpaid her for much of the 18 months she was employed.
The law student, who is 18, only received a pay slip on one occasion despite being legally entitled to them.
"I felt like if I was being difficult or asking them to do something they weren't doing, I'd lose my job. They have the power to say whether you'll get your next shift."
After a year of employment, the amount that lobbed into her bank account each week significantly reduced without explanation or warning.
"I worked up the courage to ask about it. I was concerned that maybe I had been overpaid and they would want the money back or something. In the end, I asked, they just said that was my rate of pay."
By her rough calculations, the amount she was receiving in the end was about A$16.50 an hour — well below the award rate.
A few months ago, fed up and feeling exploited, Kate quit.
"I have no way of knowing how much I was underpaid.
"That lost amount made a huge difference to me. I'm a student and that job was my only source of income. I relied very heavily on it. I had to make some drastic changes."
There's little doubt in her mind that the employer "knew the law but chose not to follow it".
In its submission to the Queensland inquiry, the National Retail Association blamed complex employment law for most cases of "alarmingly common" wage theft.
However the lobby group's boss Dominique Lamb admitted some employers do the wrong thing.
"In (our) view, deliberate noncompliance occurs out of a desire to increase profitability," the NRA submission said.
"Since labour costs are the most significant cost of doing business for a retail operator, it naturally makes sense to try and decrease this cost."
