Why did Mari, a fellow medical student with Paul, feel relief and then shame when a surgery was called off at the end of Part 1, Section 2?

The surgery Mari was to participate in was very complex and often involved a medical student standing for nine hours straight. If as the surgery was begun widespread cancer was found, the surgery would be called off. As Mari waited to see if the surgery would proceed, she had the brief thought that she was tired and she hoped metastases would be found and the surgery called off. When metastases was found, she first felt relief. Then she realized that the finding of metastases meant that the patient would die, and she felt shame.