It is possible that your cat seems to cohabitate well will this person. Does the cat have any reason to fear getting trapped there or not being able to escape easily? I adopted a shelter cat 2 years ago, she was 2. Your cat might cry when urinating or pee right in front of you to get your attention and let you know there's a problem. That's not fair to the animal. Your cat seems more like a vengeful pisser, so this might not work.
One more step
Its also only if they are left on the floor. Give them different territories until they are comfortable with each other. Now he also pees on the floor. Mum doesn't refill her dish or put it out of reach of the dogs. They are reproducing faster than I can afford to have the spayed or neutered. Have tried calming collars, sprays, feliway, aluminum foil, flower essences etc.
Cat peeing on things on the floor (weight, carpet, kidney) - Cats - - City-Data Forum
After cleaning the mattress and letting it dry, sprinkle baking soda over the spot that smells. The minute I saw the squat I fired. This is really upsetting my friend. I was 16 years old, give me a break! Sometimes that means give him a cleaner, bigger litterbox, sometimes it means more love and attention, sometimes it means Prozac.
Can't be the female in heat as all three have been fixed. I just thought I'd post an update. If the behaviour continues, he can be put on anxiety meds, but I would use that as a last resort. This had been her castle for 5 years. Mum doesn't refill her dish or put it out of reach of the dogs. If your vet tells you otherwise, seek a second opinion!