She left the school in August 2010 and signed a confidential agreement about the departure.
"In September 2010 I was at passport control at Auckland Airport heading to the UK for a friend's daughter's wedding when I was asked to step aside and was arrested," she said.
"Fraud was mentioned but it wasn't specific. Two-and-a-half hours later I was free to go. It was bizarre.
"I heard nothing until April this year when five police officers were at our door with a search warrant and three more were in the street," she said.
"We are completely innocent. We have nothing to hide. We will fight these charges."
Colleen Gray has been charged with using fake invoices from companies run by Bruce Gray to obtain $27,500 from Mayfield Primary between June 2005 and February 2009.
Bruce Gray faces five charges of issuing invoices totalling $28,750 between June 2005 and June 2008.
He submitted invoices to Mayfield Primary on behalf of teachers on the books of his companies, Teach Me and Kaizan Consulting, but police allege the teachers did not know about the invoices and the work was never done.
Court documents show that Colleen Gray is also accused of using school money for personal purchases at Mitre 10, restaurants and florists.
She is also accused of claiming expenses she had already used the school credit card to pay for, including $276 in parking tickets at Auckland Airport.
The Grays appeared in the Manukau District Court and were bailed to reappear later this month.