One - we have to remember that each cat reacts to stress differently - some take it well, others do not. Since your cat just experienced a stressful situation, the move to a new house, this could very well be the cause. However with her history of UTI, which according to my Vet is unusual at such a young age, I would first get her check out again just to make sure it has not returned. Once she has a clean bill of health and only then would I consider her problem as purely behavioral. Here are then some suggestions which I have pulled together to help figure out and correct her litter box problem.
Behavioral reasons for improper elimination can be for any of the following reasons:
Litterbox is too dirty to use. Cats are very clean and if the box is dirty they will find another place to go.
Litterbox is in too high traffic of a place. Cats won't go to the bathroom in a place that is loud or congested, so keep your box somewhere that is quiet and calm.
Litterbox is too small/large. Your cat's box should be large enough (not too large) for your cat to stand in and move around and the litter should be no more than a few inches deep.
The litter itself isn't of your cat's liking. Yes cats can have litter preferences and some of these start when the cat is young. Also don't get into the practice of continually switching brands and types of litter, this may throw off your cat's routine and confuse your cat as to where to go to the bathroom.
Your cat has recently been declawed. A newly declawed cat will not like the feeling of litter on his/her paws and may thus avoid the litterbox altogether.
Litterbox is too close to food or water. Cats will not eat and go to the bathroom in the same place, so keep these two areas separate.
You have changed the location of your cat's litterbox and your cat is having trouble finding or remembering the new place. Once your cat gets used to his/her box in one place try not to change it. If you do change the location make sure to show your cat where it is and be patient as he/she learns the new location.
Litterbox doesn't have 2 easy escape routes. Cats like to be able to see two clear directions of escape while in the litterbox, this is an instinctual feeling stemming from not wanting to be 'snuck up on' at an inopportune time.
Other cats also use this litterbox (in a multiple cat home) and your cat wants his own box. As a general rule you should have at least one box for each cat in your home.
Your cat doesn't like to urinate and defecate in the same litterbox. If so try to keep two litterboxes available for your cat and clean each often.
Your cat is in heat or is looking for a mate and is marking or spraying. For many reasons other than this one, get your cat spayed or neutered.
Your cat is overly aggressive and marking. Try to find out what the cause of the aggressive behavior is and ounteract that.
Your cat feels his/her territory is being invaded and is marking.
Can your cat see other cats from the window? Has something changed in the home?
Your cat is marking to exhibit his/her dominance in the home. This can happen when your cat is being treated against the natural cat hierarchy in the house.
Your cat has had a bad experience with his/her litterbox and is scared to go there. This is one reason why it is important to not put your cat's face in the 'mistake' and then toss him/her into the box. Any bad event surrounding the box can make your cat even more likely to stay away from the litterbox.
A stressful situation has occurred in your cat's life such as a move to a new home or a new child or cat being brought into the home. In this case you may also need to retrain your cat to go to the box.
If your cat has made a elimination mistake DO NOT take your cat over to the scene of the crime or the litterbox and rub his/her face in it and punish your cat. Many owners like to, after an accident, place the cat in the box and yell at him/her. Unless you have caught your cat in the act
chances are your cat has no idea why it is being punished, nor does it link that spot on the carpet or being placed in the box with being in trouble for not using the litterbox. All your cat knows is that using the litterbox or going to the bathroom is a dangerous event that results in
punishment. This will only exacerbate the problem as your cat will now detest the box even more.
In most cases such behavioral problems as the ones listed above can be corrected by making simple changes to the litter or litterbox. However if you feel you have tried everything and your cat simply won't use the box you may need to retrain your cat how to use the box. This is not
difficult but it will take time and patience. Reintroduce your cat to the litterbox, show him/her how to use it, giving praise and treats when the cat 'gets it right'. Note that many cats hate their paw pads to be touched
or their paws to be held, thus you can show your cat how to scratch (if he/she is using the box but not scratching) but unless your cat is comfortable with you touching his/her paws you may need to use your hand (or a scooper) as an example. Also watch your cat for signs that he/she is going to go to the bathroom, if you see the sign take your cat
to the box, and give treats when your cat finishes going in the box. You may also need to use aversion techniques to help your cat stay away from new favorite places to go to the bathroom. And make sure you clean the old area with a cleaner specially designed to eliminate caturine odor, such as Pheromone Magic - there are other enzyme cleaner, this will also prevent your cat from returning to the scene of
the crime so to speak. Regular cleaners do not do the trick. Although the area may smell fine to you, unless you use an appropriate cleaner it will still smell like urine to your cat. And if it smells like a litterbox your cat will most likely treat it as a litterbox. If you still need help correcting this type of problem you may want to consult a behaviorist.
Please do not give up on her - I am sure she is worth all the effort put in. Good luck to you and your little one.