Hi,

It's good that infection has been ruled out but what about the possibility of crystals and/or bladder stones?

If your cat has already been checked for these possibilities, I recommend confining her to one room with a couple of litterboxes filled with Cat Attract Litter. Only when she is using the boxes to urinate in every time should she be allowed more freedom. The boxes must be kept very clean as well.

Hope this works for you.

Regards,
PHKitkat