We have two female cats around four years old. Not sisters but have lived together since older was around 9 months. Cat M was neutered at 13 weeks before RSPCA allowed her home with us and cat B was neutered at exactly 6 months when we adopted her.
They both run along fine and are gentle, calm and just lovely cats- we love them to bits.
For probably about a year I thought I had been noticing spray marks on doors and things but couldn't be sure as it could easily have been a little drink or food splash from one of our small people... But yesterday I found proper evidence it could only be a cat and I strongly suspect it's cat M.
Oh wise ones, why is she doing this and how can I stop it?!