I am surviving 23 months after initial diagnosis of non-operable IHC and still going, just like the Energizer bunny (Cuz - not a word about how I might look good in pink). I have posted elsewhere about my first oncologist and her treatments and why I am on oncologist #2.
I had many of your mother's initial symptoms - heard the same story about six months if I did not start chemo. About the survival time - you can find stories here about patients who have survived years beyond what was initially diagnosed. Absolutely no reason why your mother can't be one of those success stories. As a few others have said in other topics "We don't come with an expiration date stamped on our heels."
Same issue with inexperience of the oncologist. The entire center had only seen four patients in three years. The time for the biopsy results to come back may simply be because it was done off site - shipping, handling, and waiting in the queue probably took most of that time. One suggestion - make sure any excess biopsy material is sent to which ever hospital you choose. It might save time. Also get any slides returned - all of this is your mother's body - her property, not your oncologist or the lab doing the biopsy. Might save the new onc some time.
Just to add one more on the band wagon - you need to put as many miles between you/your mother and that onc/gastro as soon as possible.
I started chemo about two weeks after being diagnosed, so you have time - don't panic. As said by others, there are many reasons to be hopeful. But this roller coaster has its downs as well as its ups for both of you. Your lives are changed. That will take time (and probably some tears) to adjust to. Normal.
Something to start immediately - live your lives. We all know there's an elephant in the room (can smell the peanuts on his breath) but that's no reason to drive you to desperation. Take time to look at the "signatures" at the bottom of some of the members of these boards - they are our philosophies. You won't find a surrender in any of them. Then sit down with your mother and write YOUR philosophies. You don't have to add them here but you will have them to help you through the dark times. Not sure if you ever saw the "Red Green Show" on PBS. One of the recurring segments has him ending with "Remember, I'm pulling for you. We're all in this together."
Peace, and good night.