Kasianni, my Thorin did the same thing. He was fine, then all of a sudden started peeing blood. We took him in, no infection. He had xrays and had Calcium Oxylate stones in his bladder and one lodge in his tube
He didn't show any signs of pain at all, my poor sweet boy. But the vet said it must have been terrible pain for him. Of course he had to have surgery ASAP. I would opt for the xrays, just to be safe (if, of course, you can afford it). Good luck and I hope your sweet girl is ok!