Sorry, adding more from that article, I had no idea about these things:
"Death from colorectal cancer is virtually always the consequence of metastatic spread to distant sites in the body such as the liver, the peritoneal cavity, and the lungs. Patients with metastases in the peritoneal cavity (peritoneal metastases, PM) have the worst prognosis.
In general, PM are under-diagnosed as their detection with routine imaging protocols is difficult, due to their small size and limited contrast resolution in soft tissues. The true incidence of PM is therefore unclear, although in autopsy series it was reported to be as high as 40–80%. The development of PM in CRC patients is often associated with a rapidly declining performance status, involving recurrent bowel obstruction, the formation of malignant ascites, visceral pain, and malnutrition. In most cases this precludes surgery and systemic therapy, leaving only palliative care to ensure the best possible quality of life."
I assume her peritoneum was not involved as they would have discovered such during the big surgery?