But when confronted, she told her victim she had withdrawn the money to buy bonus bonds.
After she complained, McCaskie admitted to police that she had also helped herself to $8000 from the bank's ATM cash float between March and May this year and tried to cover the losses by holding a false balance in her teller's cash records.
The bank dismissed her on the day of the interview.
But her latest deception was not revealed until another customer, a 54-year-old woman, read about McCaskie's offending in a newspaper and checked her bank account to find a number of large unauthorised cash withdrawals.
An audit of her two accounts found a dozen questionable withdrawals.
One withdrawal slip for $2000 had been changed to read $3000 and none of the other 11 withdrawal vouchers was completed by the victim.
In June, McCaskie admitted making eight fraudulent cash withdrawals between December 3, 2009 and April 21.
She told police she had a bad gambling addiction and used the cash to cover debt so her family would not find out.
Yesterday, her lawyer Glenn Dixon said McCaskie was "petrified" but accepted she should have disclosed her offending "from the outset".
Mr Dixon said McCaskie was dismissed from her job at a childcare centre after she was arrested.
"She was employed at the time of her arrest, but regrettably, her employer had to let her go."
In sentencing, Judge Ingram said her husband had put forward all of his finances before his resources were "exhausted" and described her breach of trust as "very considerable".
Westpac spokesman Chris Mirams said the bank had worked closely with the customer, who had been reimbursed.