The release from prison of a 54-year-old mother of 10 – after serving just 16 weeks of a four-year sentence for stealing €65,000 from an 88-year-old farmer – has provoked anger from gardaí and "devastated" the elderly pensioner.

Kathleen Lewis of Blackwater Heights, Youghal, Co Cork, had been sentenced to four years in jail, with two years suspended, after she was convicted in February on 22 of 23 counts relating to the theft of €65,000 from George Berry from Ballynoe, Co Cork, during 2006 and 2007.

Lewis was granted temporary release from the Dóchas centre at Mountjoy women's prison last week. A prison source said she had not been released because of overcrowding, but that a number of representations had been made on her behalf and it was decided she was a suitable candidate for temporary release.

"There are a lot of mitigating circumstances. She has 10 kids and 34 grandkids. She has diabetes too. A number of representations were made on her behalf by groups who deliver her services within the prison," said a source.

"While her crime was a devious one, it is not believed she will likely re-offend or is a danger. She has to sign on daily at Youghal garda station and return to Limerick prison once a week. She can be taken back in at any stage."

A garda source said Berry was "devastated" by the news that Lewis had been released after serving just four months. The decision has provoked anger from gardaí involved in the case as well as neighbours who lent Berry money, which he handed over to Lewis.

Lewis was sentenced by Judge Rory McCabe at Waterford Circuit Criminal Court on 13 May and has only paid back €18,800 of the €65,000 she stole from the pensioner.

The court heard that Lewis had threatened to take Berry to court over a very minor car collision in Killeagh, Co Cork, in 2006. The farmer told how he did not want any trouble and withdrew savings and borrowed money from friends to pay her off as she kept demanding more money.

"She took this man's life savings and is now out of prison. He'll never get that money back. He is still living with neighbours, he's in poor health and never recovered from what she did to him," said a garda source. "He's too wary because of what happened to ever live by himself again. It was a massive garda investigation with significant resources and to have the prison service just decide to let her out is a disgrace after we got such a good result and so much time was put into it.

"The gardaí are very angry about this but it was not our decision to let her out and we hope the general public are aware of that. We are also concerned that the actions of the prison service by letting her out so early sends a message to others that it's possible to get away with this type of despicable crime. It could even encourage it."

The garda added that the communities in Youghal and Ballynoe were also very upset by the recent development. "She put that man through hell. He never recovered from it. But he also had to borrow a lot of money from neighbours and friends to give her and he'll never be able to pay them back. So there are plenty of people upset by this."

When sentencing Lewis in May, Judge McCabe said he had little sympathy for her and he believed that she had no appreciation of the gravity of the situation in stealing from a vulnerable elderly man. She was "a thief who engaged in base dishonesty and despicable behaviour".

In normal circumstances, Lewis would have been due for release in November 2010 with 25% remission for good behaviour.