"Some" Bbood in Urine post Cystotomy not uncommon due to abrasion to the bladder wall from stone. Vomiting blood is an EMERGENCY I am SHOCKED to hear how dismissive they were about that. Any chance she could have gotten into rat bait? I would take her into a different vet and have them preform a necropsy. I am so very sorry for your loss. Please take care during this difficult time.