The account holders had tried to transfer about $4m out of the account, but the bank had been able recover $1.7 million.
The statement did not specify just how it got the money back.
"Westpac is continuing to vigorously pursue the outstanding amount," [of $2.3m], the bank said.
Westpac says it considers the money to have been stolen, but conceded it was human error at the bank that made the couple accidental millionaires.
The couple, who ran a petrol station, were believed to be having financial difficulties and had recently filed for bankruptcy protection for the business, police said.
Suzanne Hurring, Yang's mother, told local television networks that her daughter's actions were hard to believe and urged heer to return home.
"This was the crazy thing, she has never pinched a thing in her life - probably as a little girl, yes - but she is so honest, so honest," she said.
Hurring said she was angry with Gao and would like to "wring his blimmin' neck".