Ms Hargreaves' brother, Neville, also lived at the Western Heights home and last week locked up the house before walking to the dairy. He said he was gone for 15 minutes and returned to find every room rifled through, electrical equipment unplugged and food and Christmas presents meant for Rosalie stolen.
"Neville is on a supported living benefit and had saved food through Chrisco and it's all been taken," said their mother Jackie Hargreaves.
"They've all saved for us to have a nice Christmas so it's hard for everyone on top of all the stress and worry we are going through already."
Ms Hargreaves said they were trying to take one day at a time to support Rosalie, who is going through her weekly chemotherapy sessions. Side effects have included diarrhoea, vomiting and a lowered immune system.
"They took her Elmo present and rattle, anything to do with noises, she loves. We just were looking forward to a nice celebration to make her first Christmas a happy one," Ms Hargreaves said.
Neighbourhood Support yesterday issued an "e-crime alert" via their email network warning Western Heights and Eastside residents to be particularly careful after the areas have been targeted by thieves during the past week.
"There has also been some equipment taken from boats on properties including outboard motors, fishing gear etc," the warning said.
Anyone with information about the burglary is asked to call Rotorua Police on (07) 348 0099 or anonymously on Crimestoppers 0800 555 111.