She wiped 10 seconds off her personal best and a second off the state record with a time of 2min 37.99sec.
The St Kieran Catholic Primary School student took up the sport less than two years ago.
Club head coach Clark Carlson said it had been a concerted effort across the club to lift performances, which had paid off with some great achievements in the pool.
�Just under two years ago Andrea joined the club and started swimming in the lowest level junior squad,� Carlson said.
�A few weeks ago she broke the state record and claimed the gold medal.�
Andrea�s mum Marisa Fazari said she was proud of her daughter and it was a testament to the coaches and the club who had helped her achieve great things.
�Andrea came from nowhere and is now swimming in the gold squad,� Ms Fazari said.
�She used to go once a week and now she is going to five sessions a week.
�We are so proud of her achievements and it�s all to do with coaches who just want to help the kids go further and achieve their goals.�
Carlson said the club was one of the oldest swimming clubs in WA. It was established more than 50 years ago by local parents.
He said the club had been fortunate to acquire the services of former Olympian and Commonwealth Games silver medallist Travis Nederpelt.
�Travis is in charge of the performance squads and his experience at the top level of swimming has injected a sharpness into the training program including gym and land sessions,� Carlson said.
The club will hold an open day on Saturday, October 17, with registrations from 1pm.
For more information, visit www.tuarthillswimmingclub.org or call 0478 931 963.