It is good to know that Chloe is OK as far as the vet is concerned! Some kitties just dislike being alone - maybe Mouse is your girl's way of making sure she has company. *smile*
By the way, I have a little Seal Point girl, also named Chloe. She is now going on 17 years old and was recently diagnosed with feline diabetes. Chloe originally belonged to a childhood friend of mine who now works for a US Gov't law enforcement agency ... Laura was transferred to another country to work for an extended period of time, and since I have known Chloe since Laura and I picked her up from the breeder so many years ago, I agreed to take her into my home. She's been living here with me now for about 2 years, and has adapted quite well although it did take a while. At first, it was really heartbreaking, as she roamed the house at all hours of the day and night just yeowling her head off - I suspect Chloe was calling her "Momma Laura", and was searching for her. She stopped looking after a while - which was almost even more sad than watching her search. Recently, she began this behavior again. I observed her for a couple of days until I realized that she wasn't searching for Laura, she was trying to tell me she was sick in the only way she knew how. When I took her to the vet, we discovered the diabetes, which I am told, she probably has had for some time, only the symptoms were either missed, or chalked up to some other reasonable explanation. Now that she is being treated, she no longer displays the excessive vocalization behavior and seems to be doing as well as can be expected for now.
This is why I cannot stress the importance of regular vet visits (every 3 months faithfully!!) for older kitties enough. They mask the symptoms of things so well that you can easily miss them and if you do see them, you may think it is normal when in fact, it isn't normal at all.
Of course, you've had your girl checked recently, and I am certain the vet took blood and urine for analysis, so you are confident that everything is good. Sometimes, as I said earlier, kitties just get lonely. Maybe try leaving a radio or the TV on in a low volume overnight or when you are away from home to keep her company?
Continued best of luck,