My dog is going through the same thing. She is 11. My vet said same thing but said I could try douching her first. WOW, where do I begin.
Let me know what happens
I think you need to contact the vet and tell them about this new development. It sounds like she has an infection. Even though she's been spayed, there is a condition where if a piece of uterine tissue was missed during spaying, she can still develop a remnant type of pyometra( uterine infection, uterine tissue infection) This is a very serious and life threatening condition and needs immediate attention by the vet. As she is on hormones it's possible they may have caused some kind of stimulation of uterine tissue, and only your vet will know what to do. If it's a side effect of the leukemia, the vet will know but your dog is already ill and needs a vets care.
Valerie