That's sad to hear. After my Mother was diagnosed with a terminal disease, and having watched other family members suffer away, I've come to stop wanting to hear how long they have left total, but how many "good" months/years do they have left. Watching someone waste away for months or years in a hospital bed where they hardly know what's going on, let alone can chat with you or do something they want to do is not how I view the term "living".
Anyway, I hope that most, if not all the remaining time your mother has left can be classified as mostly "good".