My 11 yr old F beagle was thought to have Cushings disease, but my vet did not make a big deal out of it, ?

Monday AM she was fine, then after eating dinner, she started vomiting and that was all thru the night. Went to vet Tues AM and they admitted her for IV fluids and ultrasound. That night they called and said she had a kiwi gall bladder and we brought her to vet hospital. She started failing at 2 in the AM, and we went ahead with surgery yesterday morning, but she died of cardiac arrest. Is this from Cushings?