I'm confused, my mom, 84, stage4 hepatoma, dr. Gave her 6 months, it's been 3 months, she feels good one day, then bad for a week, what is that mean?

Not uncommon. You and I have good and bad days, even more so a patient with advanced cancer. My advise as a friend: rather than counting the time she has left, enjoy and rejoice with her on the days she feels good and be of assistance and comfort when she is not. My best wishes to both, god bless.