So when blood/blood-stained urine is
seen, it's hard to tell where it is
Pancreatitis, liver problems, and kidney problems, bladder tumours, stones, crystals etc, as well as a very bad UTI could all cause blood-stained urine too.
How is her temperature? Does she have a high white blood cell count?
She may need to be hospitalised while the vet runs tests. It may be better than taking her back and forth when she feels so bad. Also she may need IV fluids and/or antibiotics etc.