I had an uncle with the same form as your mom, the
glioblastoma multiforme - he also found it late and passed quickly but
glioblastoma is a different form. It is the words after it, if any, that make for prognosis - as well as stage, previous health, location of tumor and a host of other factors.
I have a cousin with a thalmic cancerous tumor, and he is doing ok so far.