Thank you for the reply.
It definitely sounds as if there is an anxiety issue as well as a possible substrate issue, which may have been solved when you went back to the finer crystals. Still, it may be worthwhile to offer a litter box buffet to identify her preference. Clumping litters seem to be preferred by most cats because it is soft. It also allows you to keep it cleaner as there shouldn't be a wet bottom. You may need to experiment with different litters, different types of boxes (short sided, tall sided, etc) and different amount of litter in the boxes. You must scoop daily! Cat's are very texture specific so look at the places she is choosing to go. If it is a carpet, you may want to put a piece of scrap carpeting in a litter box for her and slowly add more litter as she starts to use it. Some cats, mine included, prefer to urinate in an empty litter pan with no litter at all. When dealing with anxiety, even in a single cat house it is best to create an environment of "plenty” including food bowls, climbing towers, toys and resting areas in multiple locations.
Next, you want to make the other spots unattractive or unavailable, confinement is one way. Maybe keep her from the places it is occurring if possible, especially when you are not home, unless that is where the litter pans are. It may be best to not allow access to the rooms where she can look out of the windows as that maybe adding to her anxiety. Enzyme products are needed to break down the odor causing components of the urine. There are a few products that work very well to do that: Nature's Miracle® (link here), Anti-icky poo® (link here) or Zero odor® (link here) Deterrents are needed after that. Carpet runners (with plastic spikes) turned upside down work great for large areas. There are also "scat mats" which give off a small electrical charge. These are not harmful to her. Another option is an indoor invisible fence to keep her out of certain areas of the house. They are very effective. LINK HERE There are small devices that can keep her from going through a doorway as well LINK HERE. Also there are motion detector type products that work very well and are inexpensive.
I would give the Feliway another try, but maybe try a feliway collar. These can be made by soaking a cloth collar in the liquid feliway that comes with the feliway spray. I would resoak the collar every 5-7 days.
There are drugs that can be tried, but I would try the other things first. Even if you have to resort to drug therapy for a while, these are changes that should be incorporated at the same time. Anti-anxiety meds such as Prozac have been shown to effectively reduce urine spraying and marking.
This is a hard subject to cover adequately in a few paragraphs. I am including a link that may give you a few more ideas. I am also including links to a website that offer suggestions to provide environmental enrichment for indoor cats. This has become a very important subject as we have now identified that many cat behavior and medical disorders stem from the fact that they are confined indoors which is not how cats naturally choose to live. This "stress" can lead to physical and behavioral problems.
Feline house soiling
OSU Indoor Pet Initiative
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.