9 year old Chihuahua, kidney failure and heart murmur. Questions about realistic chances for positive outcome

She got diagnosed today with kidney failure. Presumed from an untreated UTI, considering her young-ish age. She also has a strong heart murmur that they noticed without a stethoscope (it was diagnosed grade 3 by a different vet in May), so the typical fluid treatment would not be viable. They gave her a small amount of fluids, and a convenia injection as she currently is pseudo-anorexic and will not take syringe fed antibiotics.

I understand that there are limited options in this situation, but do you believe this is viable enough to get her to eat again? It has been two days (today being the third) since she ate and she is understandably tired. Convenia takes a few hours to start working, but how long should i expect it to be enough for her physical appetite to return? Is there anything else i could do at home to stimulate this sooner? How long should i wait before giving up?

Are there other options to discuss trying with our vet, from your experience?

Is there any reason it progressed so quickly? She has not gotten into anything that would commonly cause this, and tested negative for common related diseases.

Her bloodwork in June came back almost completely normal, only with low platelets and low creatinine. Her bloodwork from today: creatinine 3.9, BUN >130, rbc and platelets severely low, high wbc, anemic. I'm sure some of this is expected with the anorexia.

Thanks in advance.