An 86-year-old Christchurch woman is afraid to be home alone after a brazen burglary that preyed on her desire to help.

Police have identified a 12-year-old girl who may be behind it, and a string of burglaries in Christchurch.

In this case the girl allegedly knocked on the door of 86 year old Sylvia Marley saying she was hurt and needed a plaster, but stole the woman's wallet once she was taken inside.

It's now believed she tried to pull a similar stunt on a 90-year-old neighbour two days earlier but wasn't let in the house.

Area prevention manager Inspector Corrie Parnell says the police's hands are tied when it comes to punishment because the girl is so young.

"There isn't sanctioning in the law in terms of culpability, however there's still interaction with that person in terms of their criminal offending."

Sylvia's daughter Heather says her mother no longer feels safe at home.

"Really just keep talking to her and keep telling her it's not her fault. But it's very hard, especially when they're on their own and have so much time on their own. They're dwelling on it."

Police have confirmed they've had numerous complaints of young people pretending to fund raise or faking an injury to get inside and steal.