McCabe, former head of St John Rigby comprehensive, in Bromley, south London, and a former nun, was sentenced to five years in prison earlier this month.
She was found guilty of siphoning off school funds to finance a five-year spending spree, which included expensive dinners, tickets to West End shows and a trip on the Orient Express for her parents. She also spent more than pound;7,000 on shoes.
Now Tony Marshall, her solicitor, says that he will appeal the length of the sentence. He believes that a term of three-and-a-half years would be more appropriate to the severity of the crime.
"There are no grounds against conviction," he said. "But the judge handed out an inappropriate sentence. I think he didn't like her, and didn't like the way she ran her defence. It's a very strong appeal."
McCabe continues to deny that she is guilty of any wrongdoing. In an interview with the BBC Radio 4's Today programme this week, she said: "I used the credit card as I believe everybody had agreed.
"At the end of the day, a lot of it is whether you're liked by a jury."
She insists that she spent the money on legitimate school purchases: "Those shoes were from size four to 12. They were bought for the children. The children weren't neglected. The classrooms weren't neglected.
"I didn't concentrate on the finances perhaps as I should. I might have been naive and stupid, but I didn't take the money," she said.