Your Mom is quite a woman. I had almost the exact surgery as her. They rebuilt the floor of my mouth from the skin that was removed from my neck during the radical neck dissection. One third of my tongue was removed, as were all of my lymph nodes. However, I was very lucky and did not need radiation or chemo as all nodes were 100% free of cancer.
Assure her that her talking and eating will return to a somewhat more normal state over time. Today, a year and a half later, I'm pretty much back to my old self again.
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In my thoughts