Would a repellent spray help?

Our 8 year old cart has started to wee behind the door of ‘her’ room. In this room, she has her letter tray in a purpose designed huge box to give her privacy. She also has her food and water on the other side of the room. The room is accessible to the cat but not to the dog who has been with us for 4 years. She uses the tray beautifully for her poo but I am constantly finding wet patches behind the door.
Her litter tray is cleaned daily without fail.
I read an old thread about a similar problem and I shall follow the suggestion of a feliway calmer but wondered if a cat repellent spray on the door and nearby carpet would help, but would that stop her using the room? Also are they safe for the cat? Thank you