I couldn't either.
Historically, I think she is already in the small percentiles. However, unlike most historical cases, she is in a temperature and humidity controlled environment and is not taking any exercise. Not being in the medical field, I have no idea how much that changes the cruel calculus of dehydration and starvation.
My 80-something year old aunt had a stroke and had a "Living Will." She lived 21 days with no food or water except a VERY small amount of ice chips.
She had HORRIBLE PAIN because of the dehydration. I LITERALLY BEGGED my cousins to give her food and water, but my cousins said she had a "Living Will." I felt certain she never intended for food and water to be withheld (at least not knowingly), but they went on with it.