My pet rat has blood in her urine!!!!

My pet rat is acting normal, eating and drinking normal but seems to have some blood in her urine. She always has dribbled little bits of urine when she walks around on us and has, ever since we got her. I assumed this was what they call "scent marking" but the other day I noticed the urine stream was a faded red color. I watched it very closely, gave her some cranberry juice and the next day her urine was a normal color. Her abdomen doesn't seem to be tender to the touch and she is acting normal. Everything I have read points to a UTI. Do you know of anything I can give her. I know I should take her to the vet, but I feel as though the vet is basically guessing anytime they make a conclusion dealing with rats. They are so small and our own vet said it is very hard to definitively diagnose a rat. We spent over $300 dollars 3 weeks ago on our other rat only to find out later she needed to be put down, what can I do now without spending a ton of money at the vet on our existing rat? Is this common in rats?

You need to find a cheaper vet! I paid Almost £50 on anti-inflammatories and one consultation on my first rats, but now I use another surgery out of my town, where recently i got a consultation, a course of mange mite injections and large tub of vitamin supplements for only £13.
   
I would go to the vet because they will be the only ones who have to correct medication to help your rattie.