@pizmo In my experience, age isn't always the primary factor. The general overall health, weight, and the severity of the disease of the patient are also considerations. Here is a link from Mayo's website on Capecitabine. If you scroll down, it gives you an idea of dosage recommendations. It is just a guide. I hope you find it helpful?
https://www.mayoclinic.org/drugs-supplements/capecitabine-oral-route/description/drg-20062501

@pizmo Has the doctor mentioned DPD testing for your mother before recommending a dosage? I had this testing done and it showed that I was a intermediate metabolizer, meaning my body breaks down Xeloda at a slower rate. My doctor has me on a low dosage, 1000mg daily, 500mg in the morning, and 500mg in the evening. There are three categories of how well a body metabolizes Xeloda, normal, intermediate and poor. I would ask the doctor about this testing. Below is information about this testing.
DPD (dihydropyrimidine dehydrogenase) testing is a genetic test that checks for variants in the DPYD gene prior to starting Xeloda (capecitabine) chemotherapy. It is a critical safety measure, as individuals with DPD deficiency cannot efficiently break down the drug, which can lead to severe or fatal toxic side effects.