Tania Murtagh said the 10-year-old staffy cross dog that she rescued a year ago had most of top teeth removed this month because they were rotten.
They pair had both undergone medical treatment - Rat had been to the vet seven times since moving in, including visits for the removal of the teeth
and treatment for a tumour and a toe, she said.
Miss Murtagh said she had chemotherapy this year and was battling arthritis and needed money for Rat's mounting vet bill.
A friend had created a page on the Givealittle website and yesterday $500 of the $980 bill had been raised.
She helped Rat and Rat helped her.
"I find it hard to get down and up, so she will stand beside me and I can pull myself up on her ... she means the world to me.''
Rat was mistreated after her best hunting days had past and Rat deserved to live her retirement years in comfort.
The placid dog was scared of the wind, the ocean and polka dots, she said.
She had tried to rename Rat to Holly but the new name was dropped when she failed to respond to anything but Rat, she said.