Burmese Ruby

Does my cat crazy?
I have 2 Burmese cats, sisters born and raised together, 2 years old, BOTH sterilized, never been apart. Both healthy, I've already consulted my vet about their physical health. Suddenly they have gone from being the absolute best friends hate in a matter of 2 days. Jemima, always the dominant, makes growling noises and "squawking", Ruby is cowering and hiding in terror, where they are and then they hiss and spit venomous attacks Jemima see. It is really scary. Neither pregnant, they are neutered. Nothing new has come in the house, same food as always, no pets. Neither pregnant, they are castrated. Nothing new has come in the house, same food as always, no pets.
You say that you consult your veterinarian, you have two cats together, or you just a cat? If you have just taken it to come back with a strange and disturbing smell it may have disturbed the other cat, which created problems. You could try something called FELIWAY - you can get from your veterinarian as a spray or a plug in diffuser. Cats Feliway gives the feeling of safety and security as it produces and regulates the cat pheromones cat. Especially useful if something strange has happened to upset balance. The fragrance produced is not evident to the man, so calm your cat, but does not affect you. Talk to your vet about. Good luck.