Sounds like your mom had access to top notch medical care, her medical team did everything within their power to prolong the inevitable and make her comfortable, an did their responsibility and duty as medical practitioners. Why don't you reward them with litigation?
Seriously though sorry about your loss. I understand your mourning but assigning guilt is not the right approach here. I'm a doctor. We are not omnipotent. We do the best we can every day. We take hopeless cases pour our heart and souls into it, work 80-100 hour weeks, and even in those hopeless cases where we without a doubt know we could not have changed the outcome we still assign guilt to ourselves and feel responsible for things we didn't cause. If your looking for answers how about talk with the doctor rather than speculating.