It could be a bladder infection (cystitis) If it is, it should respond to antibiotic treatment, and that may be what your vet will do first. If her condition responds to antibiotics, probably that's what is was. On the other hand bleeding could be caused by bladder stones possibly. Usually I think they would show up on an ultrasound. That might be the next move if it isn't simple cystitis.
Cystitis can be quite common in female dogs. Mine had it once, and Amoxycillin got rid of it.
When you visit the vet, take a fresh urine sample with you. Just pop a cup under her when she takes a pee, and transfer it to a clean bottle. Label it with your name, and her name.
It is possible the blood could be from her womb or vagina? Less likely if she has been spayed, but still there is a condition called "stump pyometra" where what remains of the reproductive tract after surgery can sometimes get infected. Does she have any vaginal discharge?
If she has not been spayed, it is possible she could have Pyometra. But usually that would present with lethargy, possible fever, vomiting, and almost certainly loss of appetite. Also with that usually the dog wouldn't be behaving normally, but would look and feel quite sick. That sometimes, but not always presents with vaginal discharge, often an unpleasant discharge.
The best thing you can do is keep a very close eye on her, and if she starts to show any symtoms of real illness, get her to ER or to your emergency vet as soon as you can.
I hope she is better very soon.