If you rule out a UTI I would assume that she is trying to scent Mark since she is only doing it on the beds. I have had the issue of mine who are 100% house trained pee on their beds or our bed. I don't think mine were trying to cover our scent but instead cover the other dogs scent as if to say this bed belongs to ME! For quite awhile we did not leave the dog beds down and kept our bedroom door shut and we had any further issues. Now we leave the dog bed down because of their age but it has a waterproof cover just in case.
I've only dealt with a UTI once and the symptoms came on suddenly. Squatting multiple times outside, sitting after squatting as if she was in pain, peeing frequently like every few minutes, accidents in the house. It was obvious. Maybe there are more subtle symptoms but ours seemed to start and progress very fast.