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My name is***** and I am sorry to hear that Princess is not eating. If she is as overweight as you describe, this will become life-threatening very quickly. Obese cats are prone to a condition called hepatic lipidosis, which is abnormal fat metabolism when they are in a starvation state.
Possible causes of her not eating in the first place include diabetes, bladder infection, arthritic pain, liver disease, kidney disease.
I would strongly advise taking her either to your local animal ER tonight or to your vet first thing in the morning for treatments. Hepatic lipidosis is very treatable and most cats do very well afterwards.
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