Hello, my name is***** and I have over 20 years of experience as a veterinarian.
I am very sorry that Daisy has recurrent mammary cancer and now has a bloated abdomen and foul smelling urine.
This may be related to her mammary cancer, but I would be more concerned about a reproductive or urinary tract infection.
If she is an unspayed female a pyometra (infected uterus) is a possible cause.
If she is spayed or not a urinary tract infection, crystals or calculi in her urinary tract are possible too.
She does need to see her veterinarian because if this is related to a urinary tract infection we may be able to help, and if this is a pyometra and she is not a candidate for surgery then she will get septic and suffer, so you may need to consider euthanasia.
If she were my patient I'd start with a urinalysis with culture and radiographs of her abdomen to look at her uterus, kidneys and bladder for signs of stones and the size and shape of her reproductive tract. We may need an abdominal ultrasound to identify some urinary calculi and masses in her bladder or reproductive tract.
If money was very tight and there were signs of infection on the urinalysis then an antibiotic prescription for 10 to 14 days would be reasonable to start.
If I saw lots of crystals or abnormal looking cells on the urinalysis I'd warn the owner that things may be more serious.
And I'd recommend a recheck of her urine at the end of the antibiotic therapy. If there was still blood then radiographs or an ultrasound of her bladder/kidneys is needed.
If this is a reproductive tract infection I highly recommend that she be spayed, and if that cannot be done then you may need to make a serious decision for her sooner rather than later.
All you can do for her at home is encourage fluid intake to flush out her urinary tract. Add water or low salt beef or chicken broth to her food or feed her canned food to encourage eating and increase her fluid intake.
Give her ice cubes. Offer her fresh water frequently.
And make sure she gets out frequently to urinate.
If she is straining but unable to pass urine, is vomiting, runs a fever (more than 103F rectally), has a tense, painful abdomen with gentle pressure, or her gums become very pale it is time for emergency veterinary care.
Please let me know if you have any further questions.