Anti-Aging Secret Revealed

Okay, it's settled. I have to go to France again to find out the secret of youth. Somehow, they apparently know how to look young at a very advanced age.
Is there some fountain of youth? Some beauty cream? Some food that they eat?
I am determined to figure it out.
How do I know this antiaging secret exists?
Here's a picture of Earl with our friend Marguerite when they went out to dinner along the Rue Mouffetard the other night:

Should I tell you how old she is or should I let you guess?
I'll let you guess for now.
What do you think?
Age Revealed: Thanks to everyone who guessed. Marguerite is 85.