My mother-in-law (who I call Mom since my own mothers death five years ago) is almost 70 and still teaching despite numerous health problems that have come up for her. What’s this “younger age” she is supposedly wanting to retire at?
Well as with many peoples parents who fall into health situations in their later years have you thought to invite her to live with you to finish out her days with a lesser load?
Show her another option and why it’s time for this given her health issues. It’s what we do for our parents when the going gets difficult for them. Many have done this who do not have the options of a chushy retirement plan.