Norman Krasna wrote this for Olivia...
He's the man who penned PRINCESS O'ROURKE which won an Oscar for Best Original Screenplay in 1943. With Olivia living in Paris, he wrote THE AMBASSADOR'S DAUGHTER with her in mind.
Objections to the age business are understandable, since the character more likely should have been played by someone more age appropriate--like Audrey Hepburn. But I will say this--Olivia looked very beautiful and youthful in many of the scenes and did win the Belgian Prix-Femina for Best Comedy performance by an actress for this role. All this ranting about the age factor is so overdone--she does look great in the Christian Dior outfits and John Forsythe was only a year and a half younger than Olivia. BTW, they're both still alive at this writing!
"Somewhere along the line, the world has lost all of its standards and all of its taste."