Re: Do I shoot?
I think you are okay with a half-unit dose. If her appetite is still not there for breakfast, call your vet and let them know.
It's right to fear ketones (maybe not insanely ;-) ). My GA sugarcat Bob had ketones when he was first diagnosed and spent three nights in emergency care. They showed up again just before he passed, but there were multiple things going wrong at the same time, and the ketones were just a part of it.
If a cat won't eat for 24 hours, there's something wrong that needs to be addressed as soon as possible before things go really bad, really fast.