While in another she stated: "Dad just cut cat's leg off with a tommy hawk knife, didn't hurt him cause it was dead, now the dead legs on neighbours roof looking at me ha ha."
An RSPCA inspector found Oscar in a dog kennel with blood on his open shoulder wound.
Oscar was taken to the vet and found to be underweight and anaemic.
RSPCA prosecutor Nicole McEldowney said Matthews denied chopping Oscar's leg off, saying it "may have fallen off".
In a text message the couple also admit to throwing Oscar's hacked leg on to the neighbour's roof.
Matthews was fined A$1000 ($1093) and ordered to pay another A$1100 in costs to the RSPCA, while Kinsey was also fined $1000, ordered to pay A$2800 in vet fees and handed a three-month suspended jail sentence for his animal cruelty charge.
Speaking in court he said: "I worked with race horses. I am remorseful. I considered it humane what I did. It's a one-off thing."
The couple, who own another cat and two dogs, will have the animals seized after being banned from keeping pets until the end of 2025.