My in laws bought 2 kittens several months back and one of them a grey female has had cat flu which she almost died of (better now) and rarely used the litter tray instead doing it around the house including on beds. The local vet says it could be stress due to the other animals they have (3 x English mastiffs, 1 x kitten, 1 x cat, 4 x roosters, 10 x chickens, ducks, geese etc).
So reluctantly they wanted a new home for her so we took her in.

First few days she was good as gold and used her litter tray and enjoyed being in a home with no stress. On the third night I agreed to leave the door open to the 3rd floor where all the bedrooms are and where we all sleep. This night the moment my wife and I got into bed she jumped on the bed and pi55ed on it - my side as well!!!
Now both my mother in law and sister in law work in a vets and say she did the same when she was at home. They think that it was due to my wife being on her monthly and was the cats way of protecting her.

Anyway she was put downstairs and door shut again. Now the cat never goes up stairs now even when the door is open during the day.

Yesterday morning I was going to work and the cat followed me down to the ground floor (3 floor townhouse). The litter tray is by the front door and while I was getting my coat on she scratched the door mat then done her business on the door mat.
The same night I was in the office (Which is right by her litter tray) and instead of doing it in her litter tray she jumped in our silver cross buggy and did it in there.

My wife has just told me that she has done it again in a wicker basket by the front door (litter tray is about a metre away).

Now there are allot of cats in the area and she has not been spaded yet (booked in on Monday as neighbour said she could be coming into season) we have two young children who can also be over friendly with her.

Is there a reason for her doing this? Do some cats just do it and won't change, Is she in season and not spaded, marking her territory, doesn't like to do it in litter tray if people are there.

Having her in our home was to see if having no 'stress' stopped her doing it and until yesterday she was doing great apart from on the bed. In laws said they would take her back if she continued to do it. I'm not the biggest cat lover but my wife and kids love her but I can't take her pi55ing everyday.

Any ideas or suggestions.

Sorry for the long rant but thought best to give all the facts.