Renzo,
While my Mom's death was quite peaceful, there can be unforeseen complications, too. My Mom was hemorraghing in the week before she was dying. It came out as what appeared to be a very loose stool, but was in fact, blood. We kept giving her blood transfusions as the Doctor indicated that she might have an infection. While this was difficult to handle, the doctors and nurses were very professional in their handling of things and eased our fears.
One thing that you should be aware of with cancer is that a pulmonary embolism is possible at the end of life. We were quite unprepared for it and I have to say that I absolutely panicked when I saw the blood. The nurses bring in a red towel to help absorb it and so that it is less distressful to the family. We were also assured that my Mom was quite beyond awareness by that time, so while a painful experience for us, it was quite peaceful for Mom.
As the hours went on, we kept the room very quiet other than to murmur sweet nothings to Mom. My brother and I both heard the cadence of her breathing change, signalling shallower breaths and stayed with her until the last involuntary breaths where the body is ensentially clearing itself of air. It was quite peaceful and in its own way, beautiful, too.
I wish your Mom, you and your family God's comfort at this difficult time. Peace be with you all.