Gerrard did not go to work and advised her manager she would not be returning.
"That is understandable given that during the period you were away from work, you and your co-offender were helping yourselves on numerous occasions to the bank account," Judge Dugald Matheson told Gerrard.
Gerrard's ex-partner Damien Hakaraia was sentenced to 22 months' imprisonment in July for 22 charges of using a document to obtain pecuniary advantage.
"It's a gross breach of trust against a vulnerable patient in a rest home," the judge said.
Judge Matheson said the victim had "suffered considerable loss — fortunately that loss had been remunerated by the bank".
For Gerrard, lawyer Stephen Ross said police agreed her involvement in the offending was to the extent of $9000 spent.
Gerrard was convicted on a charge of taking a document for the use of gaining pecuniary advantage and 15 further charges of using that document to obtain an advantage.
She was sentenced to four months' home detention, Judge Matheson taking into account that she had been in custody from March until July.
The judge said Gerrard needed to work on her alcohol and drug addiction problems.