Update! I fed Newt a few small pieces of chopped porked ribs as a test - she loved it! Practically ignoring the canned food. But, she drags the meat from the food mat onto the floor when she eating it, and when the kittens get close, she growls (like a dog) and hisses at them, at which point the kittens beat a hasty retreat. Seems a little strange to me as they all get along when eating canned food and kibble.
How do I get Newt to share the raw meat? The kittens are usually pretty daring when playing with mom and will pounce and annoy her to no end, but her reaction with the raw meat seems to have sent a pretty strong message to the kittens, and they didn't go anywhere near her.