I would get her checked for a UTI. When I got Kobi he had a URI, which got treated and a couple weeks later he started peeing outside the box. It was only happening every couple days, combined with his age (also about 14 weeks), I thought it had to be behavioral. But after making many changes (adding boxes, changing litter, etc.) I finally took him in and sure enough it was a UTI.
Also, make sure you're using an enzymatic cleaner like Nature's Miracle and really soaking the area when cleaner. The enzymes break down the urine to eliminate the smell, otherwise the cat will still smell it even if you can't. Since she's been peeing on soft furniture, the urine will spread out in a pyramid shape the more is soaks into a cushion or mattress. So a nickel size spot on the surface may be a couple inches wide further down. Make sure to pour at least a half a cup of cleaner on the spot and let dry.
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Holly, Misty & their friend, Jake, the dog.
Onyx, Callie May, Maggie & Kobi forever in my heart.
Yes, I know I need a new signature pic...someday...