Hi, please help if you have any type of cat with this situation!
I have a 2 year old female bengal cat who we have had for about 6 months now. She has settled in amazingly into the family and we have had no problems with her at all - until now.
She was never shy or nervous when we first got her and she was never bullied by our other bengal girl (same age) they get on great and are getting closer as time goes on.
She was neutered right before we got her and she is up do date with all medical vaccinations etc. She is extremely affectionate, loves to play and follows us everywhere. She is a complete indoor cat even though our other bengal is indoor and outdoor. She a few months ago she got out of the house and went to explore around our estate and didnt come back for a day or two. She did this twice and we were nervous as she had never been outside on her own before. Now she wont go outside the back door unless its a few steps before she comes back in, but altogether she is a very content cat inside.
Expect recently we have been getting very strong urine smells in the house. We've cleaned up again and again but she keeps doing it. I presume it is only spraying because we dont find any puddles but it is a lot as its all over the house. We have had to stop letting her upstairs at all (she used to sleep upstairs at night without any problems) because she was urinating in the bedrooms. We have nearly tried anything at this stage. We have tried sprays, getting two litter trays and at this point we dont know what else to do because she is destroying our house. We REALLY dont want to get rid of her as she is the most beautiful cat ever but this cannot carry on the way it is.
Does anyone have ANY suggestions?
Thankyou

Get her checked by the vet first of all, if she has a urinary problems then that can be a cause of sudden toileting issues.

I think I know what the problem is, as I have the exact same issue with my Bengal.
The problem is the other cat being able to go outdoors. You'll probably find most of the spraying will occur shortly after the other cat returns from being outside. The cat will have outside smells, and Bengals being quite territorial, will mark their territory, even females.
Does your indoor cat has a favourite pet blanket she sleeps on? When the outdoor cat returns, rub the cat with the blanket to transfer the scent from the indoor cat and your problem should gradually go away.

I agree with David. Sounds like a territorial problem.
However, a visit to the vet is always a good idea to see whether it is a medical problem.
Otherwise, it is territorial in my opinion. A cat will spray when its 'area' feels compromised by other cats. Maybe roaming neighborhood cats are causing the problem, but it could be related to your other cat being allowed outdoors. The smells from outdoors are being transferred directly into your indoors cats space.
I suggest always having enough litter boxes (And don't place them near windows or open doors where your cat might feel vulnerable). The formula is one tray per cat plus one. Also make sure you clean the sprayed areas very well to eliminate any smell. Maybe a pheromone diffuser would help with the smell that is distressing your indoor cat.

I don't think you need to worry about re-homing her at all!
I have read a great book that deals with spray in depth in one chapter. Pretty useful. [ Cat Detective: Solving the mystery of your cat's behaviour by Vicky Halls]

All the best :) Meg