Cat sudden frightened behavior

Tonight, my dog was outside and I left the back door open for him to come in. We heard our cat hiss and angry meow then ran and hid. I ran to the door to see what was out there and there was nothing, the dog had come in and was calmly laying on the floor. The cat would not let any of us near her and hissed and growled everytime anyone would walk by. At one point the dog was walking and she chased him and started hissing and meowing at him. She is 2 years old and they have been together all this time. Could she just randomly been spooked by the dog? Will this likely pass, my kids are worried to death about her.

Answer by Kate
hi yes it sounds like something frightened her. It could have been the dog, it could have been a strange smell outside. In fact even the tiniest of things can do this.

The behavior your cat is displaying is called aggression trauma and is not uncommon. Normally it will pass in a few days once the cat has over come the fright. However if it is severe she may need a period where the cat and dog are reintroduced in a safe controlled environment for a few days. the process is described here

https://our-happy-cat.com/introducing-cats.html

Don't worry it should pass

best wishes Kate

---