Jessica Camilleri was covered in blood when she knocked on her neighbour's door in Sydney's west close to midnight on Saturday.

Ali Bostani had heard screams for help moments before the knock on his door. When he answered, Ms Camilleri allegedly told him she'd just killed her 57-year-old mother.

Rita Camilleri's head was lying nearby on the St Clair footpath.

"She said, 'I need help', I said 'what sort of help do you need?' She said, 'Call the police or ambulance.' Her face was full of blood ... she said, 'Yeah I had a fight with my mum, I killed my mum,' " he told the media on Sunday.