No, I don't think you are wrong. Especially when you consider what he said on the report. He said that she had irreversible liver damage. How would that get her some time off from work? Terminated maybe, but a vacation not likely. Strange story.
I'll wager The Doctor gave her the diagnosis in writing for her to get a disability pension. Probably a kickback involved.
She was German. It's almost impossible to fire anybody in Germany for any reason. A report of terminal illness would just give her an excuse for multiple vacations for 'treatment'.
In most of Europe, it is common practice for doctors to sell diagnoses, since all the medical care is 'free' anyway.