In one of her deceptions, Bourton allegedly defrauded one customer of $472,000 during her employment at the bank between early 2005 and late 2006.
She created fake accounts with large overdrafts, and established overdrafts on the man's existing accounts, from which she could draw the money, the Crown said.
But she allegedly paid the man back $155,000, including $55,000 of someone else's money, and moved more than $583,000 of his money between his four accounts as she tried to hide the fraud.
The court heard she took $29,700 from the man's personal cheque account to buy a commercial property on Lake Rd.
But when settlement of the property fell through because of insufficient funds, Bourton allegedly established a $100,000 overdraft on one of the man's accounts and took $98,000 of it to settle the sale.
The Crown also said Bourton got two home loans in the name of the man's family trusts for $214,000 and $100,000.
She tricked the man and an independent trustee into signing the loan agreements and then used the money to put $214,000 on to one of the man's accounts to reduce the overdraft and using the $100,000 to disperse between his other accounts to cover money that had been taken.
By October 2006 Bourton's actions were being investigated by Westpac where she had lost some privileges, including her credit approval limit, Ms Mann said.
In late December 2006, after resigning from Westpac, Bourton met her former client and offered to help him get finance to buy a business in Ireland, for which he would need to give her signing authority on his personal cheque account.
But the Crown says that without his knowledge she got signing authority for all four of his accounts.
She then flew to London, leaving behind $316,000 of her own overdrawn accounts. Ms Mann said Bourton made a series of internet transfers on the man's accounts without his knowledge.
Another client met Bourton at a dinner, and moved his banking to Westpac so Bourton could manage his affairs. She allegedly took a total of $115,000 from the client.
Bourton was arrested in July 2009 when she returned from Ireland, where the Crown alleges her offending had continued.
The trial is set down for at least three weeks.