She is about 7 months old and was spayed about 2 months ago.
She had a litter tray indoors until she was spayed and then I started to encourage her to use the cat flap. It took her a while to learn but now she is fine with going in and out. Once she had mastered the art of the cat flap, I moved her litter tray to outside the door in the garden, with the idea of gradually moving in further away from the house and mixing in soil from the garden.
She suddenly developed a habit of going to the toilet in the evenings only in our front room in the corner. I moved the litter tray back indoors thinking that she was scared to go out in the dark and use it but she is still doing it. I realise she may well keep smelling the scent and thinking she has to go there again, but I don't know really what to do. I spray with antibacterial spray after I have cleaned up but there is only so much I can do with a real wood floor which has probably absorbed much of the scent.
Stress perhaps? Cats will often spray when they are stressed and it could be a number of things causing this. A new cat in the area, a minor change in your lifestyle or routine. If it is stress a feliway diffuser is your best cure to relax your cat. They really do work but sometimes I think you need to get a normal feliway spray just to get a boost to start it working.
As for the area your cat has taken to going I have heard that using citrus smelling cleaning liquids is the best way to stop the cat going back there. IME though it doesn't work. I've lived in many different homes and when my cat picks a spot the only way to stop it is to put something in the way!
I was just about to come and ask a similar thing. My two boys who are about 24 weeks old and neutered, have taken to pooing in the house. One does it in the bath, the other who has more self control did it last night by the washing machine. Any ideas how I can stop them? They don't use a litter tray any more, there aren't any other cats (that I've seen) around us so I doubt it is fear.