Hi, thanks for healthcare magic
I am sorry for the pain that you and your family must be experiencing.
As you correctly stated, it is difficult to estimate the time your sister has left.
When a person has a 1 to 2 weeks left the following may be seen: mostly sleeping, disorientation
, altered perception, there may be skin color changes, increased perspiration.
With a few days to hours the breathing may be very irregular, there may be episodes of no breathing followed by fast breathing, unresponsive, hands and feet may look blotchy.
I hope this helps and wish you and yours the best