We moved house a couple of months ago and my previously indoor cats have started to go outside. Ever since we started letting them out my female has become very aggressive towards the dog, the other cat and my DD1 (19mo).
She is mainly ok with adults that she knows, and doesn't seem bothered by the new baby. She does hiss when strangers come to the door (more effective at warning us of visitors than our golden retriever) and this is also new behaviour.
At first I thought she might be in pain, but she doesn't seem to be. It's a nuisance as she really makes a lot of noise and DD1 doesn't understand why she is suddenly being so nasty. I can't see any evidence of injury or having been in a fight. She used to be really sweet with everyone, though capable of standing up for herself if need be.
Any ideas?