his reaction seems quite normal to me, given that cats in the wild mark their territory with urine - so when he smells Jezabel's he is naturally wary - so another thing you could try is adding some of his used litter to her tray, and vice versa, to mix the scents up
another thing you could try, assuming it's an open litter tray, is swapping it with a covered one, to minimise the smell of the litter