She debited the bank account of an elderly female customer to the amount of €303,500 to buy a bank draft which she made payable to the firm of solicitors who were dealing with the sale.
She then drew a further €2,516 from another account to buy a bank draft to cover her own solicitor's fees.
The court heard that three months later she drew €16,445 from another customer account to clear her partner's car loan with Volkswagen.
Halpin, a mother of a six-month-old son, has since handed over the deeds of the house at Beverton Gardens, to the investigating garda, Detective Garda Peter Meenan. The house is vacant and she is back living in her family home.
She pleaded guilty at Dublin Circuit Criminal Court to two charges of stealing a bank draft from Ulster Bank, Blanchardstown between September and December 2009.
The charge relating to the smaller amount was taken into consideration.
Det Garda Meenan told Colm O'Briain, prosecuting, that Halpin had been working at the branch for seven years as a customer service officer and as such had authorisation to access what are termed suspense accounts.
This is an account in the bank which holds temporary funds, which may be in dispute, before they are analysed and transferred to the appropriate customer account.
Det Garda Meenan said Halpin used this account to then cover her tracks and "effectively fill in the holes" that had arisen out of her stealing the funds from the customer's accounts.
The irregularities came to the bank's attention in January 2011 and Halpin was immediately identified as the culprit as she had used her own username and password to complete the transactions.
She made immediate admissions and said none of her colleagues nor any family members or friends knew what she had done.
Halpin told gardai that her partner of nine years had no idea that they had been refused a mortgage.
He later told investigating officers that she claimed she had won the Lotto, which was why he was not surprised to see that no mortgage repayments had been made.
Det Garda Meenan said Halpin has no previous convictions and was unlikely to come before the courts again.
He said that she was fired from Ulster Bank in March 2011.
Garda Meenan agreed with Ronan Kennedy, defending, that no customers at the bank were ever at a loss because Halpin had used the suspense account to refund them.
Det Garda Meenan accepted that it was "only a matter of time" before Halpin would be caught as she had used her own unique staff number to carry out the transactions.
He further accepted that she was genuinely remorseful and that her partner and family were in "complete shock".
Mr Kennedy said the property is now worth about €210,000 and that Halpin hopes that the bank will take that as recompense, in addition to €30,000 she had in court.
Judge Martin Nolan accepted that Halpin was "an exceptionally good person" and that she had been under pressure to close the deal on the house.
He said it was unfortunate for her, her family and young child but said she must go to jail.