@edios1, I hope you saw the helpful post from @ken240.

Edios, your mom must be grateful to have you help with the research and decision-making. I have to agree that getting a second opinion would be wise and hopefully helpful in her situation. To help further give confidence to that decision , you might be interested in this research on the value of second opinions that Mayo did:
– Mayo Clinic researchers demonstrate value of second opinions https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-researchers-demonstrate-value-of-second-opinions/

The rising tumor markers are confounding. But you're quite right that CA 19-9 levels alone are not typically used as absolute evidence of the presence or the absence of malignant disease. The test is used in conjunction with information from the clinical evaluation of the patient and other diagnostic procedures. @davidgg had a similar situation and may be able to share more.

You've likely seen this already, but here's further info about Cancer Antigen 19-9 (CA 19-9) https://labtestsonline.org/tests/cancer-antigen-19-9

Have potential conditions like cholangitis (infection of the bile ducts), pancreatitis (inflammation of the pancreas), cirrhosis of the liver and bile duct obstruction, such as from gallstones been ruled out?

Kudos to your mom for prioritizing her health, reversing her diabetes and staying active. This news when she is feeling so well must be a real punch in the gut. Tell her to keep up the great work. Being as healthy as she is now will serve her well whatever the outcome of these tests.

I'll be interested to hear at the second opinion appointment next week.