Only, she isn't herself because her behaviour has changed.
Have you tried different litter trays?
Personally, if that were one of mine I would be looking at whether or not she could get into the litter tray (and experiment as such, trying lower sided things- something like an injury or arthritis might be a possibility) and if she could actually hold her wee look enough to get in there.
I personally would cover the floor with something water proof, like tarpaulin, and then use something over it that was washable, to soak up any urine, so that it didn't matter a huge deal if she didn't go in the litter tray.
At a regular six month health check they might be unlikely to find anything unless you specifically asked them to look for it, and maybe not even then. It took me several visits to finally get Sky's arthritis diagnosed, for example.