It is difficult to assess want your doctor's have in mind with all the medical problems and what has priority, etc. Regarding a eluded stent implant there is a risk for clots for up to a year or so and aspirin and plavix is prescribed to help prevent clots. If there is going to be an operation, there would need to be a halt to anti-clotting medication with stent implant and a riks of a heart attack or other emergency intervention to prevent excessive bledding.
If there is chest pain (angina pectoris) from the implanted stents, then there would be a restenting procedure or something else such as a bypass. The risk for clotting with a drug eluded stent is very low and if the pain can't be controlled, then there could be a decision for intervention of the medical problems that exist!?. A treating doctor should know what are the priorities, what is the risk vs. benefit for intervention, etc. There should be a discussion with the doctor regarding medical treatment priorities, what is the treatment proposed going forward, etc.
Bowel obstruction may require an emergency operation, and even doing a colonoscopy is a risk when there is anti-platelet medication in the system. Sorry to hear of your sister's medical problems and the medication may be intended to delay any intervention until a less risky time becomes available.
Thanks for your questions, and if you have any further questions or comments you are welcome to respond. Take care,
Ken