At this point, all we know are the outward signs -- the aggression, the unprovoked biting, the screaming. These signs are consistent with either a physical problem causing her pain, or an emotional problem None of us can tell. And it could be a physical problem at the root, that has been complicated by other events (Connor's arrival, the long period of isolation, the flight over here, Jenn's other cats, maybe even something like the different sun angles and different light intensity compared to Bahrain).

It's possible something happened to her right about the time that Connor arrived, and he might really have nothing to do with her problems. Just to throw out some examples (without implying that any of these might be real), she might have been stung by a scorpion (or bitten by an insect carrying disease, or snake), and the venom might have caused a problem, she might have had a stroke, or maybe she gets a cat-equivalent of migraines, or any of many other possible conditions -- some of which could easily have been missed in a routine vet exam.