There are a lot of things going on in this post so I'm going to try to address them all.
My mom has had numerous surgeries over the last few years - intense caridac surgery (repair of ballooned heart wall, then 10 yrs later aortic valve replaced),, hip replacement (both hips), ovarian & uterine cancer surgery (hysterectomy) and eye surgery, etc. My husband had spinal surgery behind his neck becuase his hands were not properly working due to spinal damage from a car accident. From what I've lived through, the more intense the surgery, the less chance that the patient has any idea or recollection that you're there or not. For my mom's latest heart surgery (3 years ago) we did not stay at the hospital - you can't go in to see the patient for many hours afterwards and even then the patient is completely blotto and doesn't know or remember that you were there. A few days later when my mom was a little more with it - but still in bad shape she said "I thought they said I wouldn't be awake right after the surgery?" she had lost a day and was certain that the afternoon & evening the day after the surgery was the same day of the surgery. (They kept her really snowed that day.) When my husband had spinal surgery (in the city) (NY) and he wanted me to sit in the family waiting room all day. Knowing what I knew about how long surgeries take and how many hours it would be before they'd let me see him, I waited about a half hour then went for a walk along the river promenade, then went for breakfast. When I got back to the family waiting room I still had time to read a book and scan a few magazines before I was able to go see him in recovery - for 5 minutes. They had him up and actually moving around - he talked to me, told me he had feeling in his hands, again, then fell back asleep. The next day he had no recollection that I had been there.
Waiting at the hospital is more about the family members than the patient. The doctor can come out and talk to you in the waiting room or he can give you a call. Assume the very worse thing happens - what will the difference be if you're an hour away or in the waiting room? Can you do anything to change the outcome? Of course, not. In one of the large university hospitals around here the doctors don't even come down and talk to you - they call the family waiting room and talk to you over the phone. It would work just as well as if I was at home.
I've waited at the hospital and I've gone to work and I've also gone shopping during love ones' surgeries. It was way worse waiting at the hospital. The chairs are uncomfortable, there's nothing to do, there's no benefit to the patient, there's too much time to worry instead of being distracted, etc. BUT - if it makes you feel better and puts you at ease, why not?
As for the boss, maybe he's been there like I have and thinks sitting at the hospital is just counter-productive. But - if your friend has days off that she can take why doesn't she just take those days off?
Also you asked about cancer, and opening up the patient, if it makes the cancer spread. There's nothing about the air, or the surgery that makes cancer spread. Assuming the cancer is going to spread, usually by the time the cancer is detected and surgery is required the cancer has begun to spread any way. If there's anything it could be argued that the healing process after surgery makes a person's metabolism speed up to heal, which could, maybe, perhaps, cause the cancer to grow more quickly - but there's nothing to really prove that. If an oncologist want to do the surgery it's becuase the cancer must come out. If it's in the lymph nodes the cancer has already begun to spread. The good news, however, is that cancer treatment has imroved so very, very much that people who used to perish now go on to live quite a while. My mom was diagnosed with ovarian cancer more than 6 years ago - and she's still with us. It use dto be a death sentence - now it's chronic care. A person's outlook has alot to do with how well they do after a cancer diagnosis