Are you sure that she doesn't have a urinary tract infection? It could be that it burns when she pees and she is afraid to do it. She could be extending her bladder.
I would get one of those things that you put on the toilet that catches urine (get them from a medical supply place) and make it so that she pees in it the next time she is willing to pee. Make sure it is disinfected clean first. put it in a sterile jar, into the refrigerator, or take it directly to the ped's office for testing. If you don't or aren't able to get a urine sample, they may have to put her to sleep and cath her.
Make sure that she is getting plenty to drink. You may even need to tie drinking fluids (specifically water) to her getting to play with her toys or doing a favored activity. Not drinking enough is hard on her kidneys and can cause crystals to form, cutting those delicate tissues, which shows up as blood in the urine. (Not necessarily blood that you can see. If it actually gets to the point that you can see it, it's pretty bad.)
So get that urine sample, and then get her to the ped. Let us know how it goes, okay?
Dawn