I truly believe Tiffany is terminal and is in complete denial. I think Amma and Matt know this or at least suspect this as well. I think Amma and Matt just agree with everything she wants to keep her happy and pacify her, sadly.
My ex-husband's father died of colon cancer. He was the type who never went to doctors. He had a lot of abdominal pain. He had so much pain one day, he couldn't have a bowel movement. He had to go for an emergency colonoscopy. We found out he had a tumor so large it was blocking his entire sigmoid colon. They could not get the scope past the tumor without it bleeding. They then reasmoved about 6 inches of his colon. Unfortunately, it was too late as the cancer had spread to his liver. They tried a round of chemo and radiation but nothing was working. He was moved to hospice after about 2 weeks at hospital and about 3 weeks at home. After 1 week in hospice, he passed away.
I also lost my father to stomach cancer so I am quite familiar with this nasty disease. I have a bad feeling about Tiffany. I suspect they cannot get past the tumor with the scope. I think if they tried, she would bleed excessively and in her frail condition, that could be very dangerous. The surgeon probably saw how large the tumor was and felt it wasn't worth doing the biopsy. Her constantly being on morphine was just like my father and father-in-law at the end. Neither of them could go without morphine as the pain was too much. This might be TMI for some people, but the oncologist told us that if he did not have the tumor removed when he did, he would not be able to have a bowel movement and would throw up everything he ate because the tumor created a blockage. He even mentioned that some patients even start vomiting feces at the end due to the blockage. Colon cancer is a nasty disease. Also, her being tired could be because of internal bleeding at the tumor site. A lot of people with colon cancer will have anemia from the tumor bleeding internally.
I'm sorry to say, but I think the doctors now know she is terminal and are hesitant to tell her because of her mental instability and behaviour. I feel so sorry for everyone involved in this including Tiffany. She is a royal pain in the butt but I think when she finally realizes her true situation, it will destroy her mentally and maybe even physically.