Hi there

so sorry to hear of your mother's diagnosis. My mum was diagnosed with advanced bile duct cancer last December and passed away a few weeks ago. Yet I am still googling and searching forums on Bile duct cancer.. perhaps my way of grieving and remembering mum.
One of the first two symptoms she had even before her diagnosis was pain in the upper stomach area and frequent diarrhoea. 
 

The indigestion and diarrhoea& constipation didn't really get any better as time passed. Puréed pumpkin was something she found easy to eat.. anything that is bland and gentle on the stomach. Oily (or anything with oil?) and fibreous food would be the worst. She found protein difficult to digest although we were keen for her to have some as she was losing weight & muscle rapidly. For the constipation it was important that she moved and exercised gently (like walking) as the build up of gas in her stomach was causing pain.

I am sorry that your family are going through this and your poor mum is feeling so anxious. If you find it helpful to hear more of my mum's experience please ask. I would like to help in anyway possible. 
 

J