Yes you need to get her ASAP to a vet, it is very important, my Lexie had one a few months ago, and was put on antibiotics and was fine, you have to be aware they can have crystals and that can be more serious , and as your kitty is older you need to keep a good eye on her well-being, also if you or your mother has ever experienced a UTI, it is extremely painful, no different for a kitty, so please don't hesitate and get her there promptly, good luck.