Dead fucking serious.
The only hope she has of securing her future is to make sure his kids can't wipe her out if he dies or becomes incapacitated. And she should be working toward developing marketable skills and getting some real world work experience.
These May/December things can get ugly as hell when December has kids the same age as the new spouse. And when the older partner wants the younger one to stay ignorant and placid, bad sign.
If he refuses to do a post nup -- he can amend his will but he can also go back and change that without her knowledge; he can get life insurance but if he doesn't pay the premiums the insurance company won't tell her and can't give her information -- the only protection she has is to get her name on the deed (which can't be removed without her knowledge) and a child. At least if she has kids the odds are strongly against the courts putting her out of the home in the event of something unforeseen happening to her husband.