Hi
I’m sorry to hear this. I’m aware and how upsetting this can be!
It’s very likely that her behaviour relates to the loss of her sister with anxiety being the base cause. I’m presuming you mean that she is urinating outside the litter tray. This is usually termed misplaced urination. However misplaced defecation (pooping outside the litter tray) is also quite common. Both of these problems are commonly directly behavioural problems seen in cats suffering from anxiety. The cause of the anxiety is commonly disruption within their immediate environment such as the loss of a companion or the introduction of a new cat (or a new neighbourhood cat). Sometimes when the problem is purely an inappropriate urination issue it can relate to a urinary tract infection (UTI) which in turn can be triggered by the anxiety. For that reason, if her problems are with urination I’d recommend that her urine be checked by your vet.
To tackle the problem we need to act in two ways:
By mechanically I mean primarily have multiple litter trays available and keep them clean as cats prefer not to use soiled litter. Use soapy water to clean the litter trays and don't clean up any "accident areas" with strong smelling cleaners (particular ammonia based) as that can start a cat spraying. If it is at all convenient, temporarily place additional litter trays at the frequently used incorrect sites. You can then gradually move them day by day back towards a convenient location.
You are obviously getting towards the end of your tether with her and considering re-homing her. But you are right with your thoughts that that may simply make her worse and pass the problem onto someone else. Her anxiety will just become greater in a new home. If you are prepared to try a little bit longer with anti-anxiety thereapy it’s well worthwhile. There are two products that can be effective for this. The first is Feliway. This is available on the internet, at pet supplies and from your vet. It is a spray or diffuser that contains pheromones. Cats produce these chemicals from specialised glands in their chin and lips. This is why you will see them rubbing their face on household objects, effectively marking these as "safe zones". You can use the Feliway to mark your home as such. This reduces the anxiety. The product is safe and odourless to humans. It’s well worth trying. http://www.feliway.uk.com/ The other product is Clomicalm. This is an anti-anxiety medication tailor made for this problem and it is almost certain to fix the problem. However it requires a vet visit. If you are in the USA it isn’t registered for cats (just dogs) but this is a licensing issue. It is used all around the world in cats and most US vets will prescribe it. It must be used for several weeks to have its effect so I generally use it in combination with Feliway. http://www.clomicalm.novartis.us/qa/qa.htm
Remember that her behaviour is anxiety related so try not to upset her by showing anger. Unfortunatey locking her in the laundary may even be contributing to the problem.
I hope I’ve been of help with this frustrating problem.
Kindest regards, XXXXX
Cat Veterinarian
Bachelor of Veterinary Science University of Melbourne