Are there chances of my grandmother getting a heart attack in the middle of a stress test?

Hi doctor,

I am worried about my grandmother. She is 80 years old. She has done some stress tests eight years back. Two years back, she got chest pain and heart attack while doing stress tests. Now, she is advised to do stress tests again. Her blood pressure remains fluctuating. She is weak and pale. She had chest pain frequently before few days and took Nitroglycerin under the guidance of the doctor. When she consulted a cardiologist after few days, he advised her to do cardiac catheterization to adjust some of her heart medications. She was advised to take Nitroglycerin while having chest pain again. After having three episodes of chest pain, she was advised to come back to the hospital. We accepted to do it. After getting the results, the cardiologist told me that she has a kind of an obstructed artery. There is blood flow and it is not completely blocked. He advised doing open-heart surgery for my grandmother. But she has done it before twenty years back. She has undergone a bypass and placed three stents. She has type 2 diabetes. The doctor advised her to take a clean diet. After doing cardiac catheterization two years back, she has not done any stress test. She has done only a heart sonogram and regular checkups with her PCP and cardiologist. My grandmother says that she does not have any chest pain for more than a year. I do not want anything to happen to her during stress tests. Though the risk is low, I feel that she can have a low percentage of having a heart attack during the middle of a stress test. The doctor clearly told me that she can have an outcome while having a stress test. I think that it can be too risky for her. I need a second opinion.