Why is my dog vomiting yellow bile and kibble after UTI meds?

Antibiotics and urinary tract infections themselves can both cause nausea/vomiting. However, as you finished the antibiotics 5 days ago, it is less likely that the vomiting is due to the UTI antibiotics. If she has recently gotten table food or had access to food from the garbage, she may have a condition called pancreatitis caused by a sudden high fat meal that may cause vomiting, diarrhea, abdominal pain. A trip to your veterinarian for screening bloodwork to rule out a liver/kidney/pancreas issue as the cause of the vomiting, subcutaneous fluid therapy, anti-nausea medication (cerenia), and a prescription intestinal diet is advised. If you are not able to get an appointment immediately, I recommend feeding only a bland diet of boiled rice and chicken (with no regular kibble) for the next 3-5 days. Sometimes this alone helps resolve the symptoms of mild gastroenteritis. Good luck!