Given that your grandmother is 88 years old with oxygen-dependent severe chronic obstructive pulmonary disease (COPD), her risk of any type of surgery will be high, especially with a major procedure such as fractured hip repair. Her aortic aneurysm is relatively small at 3.5 cm, I assume you meant cm and not mm, and poses minimal risk.
The first thing you should do is to have a frank discussion with your grandmother about her desire for surgery. Is she currently ambulatory, even minimally so within her own residence? If she is not, you should discuss the rationale for surgery, with the doctor(s) proposing it. The benefit may not outweigh the risk of death or serious morbidity. If there is agreement that the risk is worth taking, you should ask the surgeon if there is more than one surgical approach which would pose the least risk and/or the greatest benefit.
In one study of people 90 years old or older who had hip fractures, those who had surgery and survived beyond the immediate post surgical period, a greater percentage of them were alive after 2 years than the group that opted not to have surgery. You should also discuss this with your grandmother's primary care physician.
Good luck.
i had just come out of a week long coma, when i had a hernia that was strangling,
i had cronic pneumonia, a trachea in my neck, tubes coming out all over the place,
they said it is a emergency operation, i asked as best i could if i was strong enough to cope with this operation they said yes, i was very ill at the time, but survived ok,
so i think you can say if they thought she was not strong enough to cope they would not do it.