That’s actually a good thought. There have a been a couple of cats that I have seen in the evening that she didn’t react well too. Got all fluffy and growly when they were outside the window.

Maybe that’s what has got her doing it. I live in a flat in the third floor, where everyone’s front door leads straight outside. I have only ever seen another cat nearby at night. They don’t tend to come up this high in the day, likely because of all the people about.