Princess Diana with… Princess Grace?

Princess Diana, at right in the handsome black gown, chats with someone who either is Princess Grace of Monaco or looks very much like her. (The original caption doesn't say which.) Prince Charles stands by at left with a piece of paper, possibly a note from a courtier reading "We suspect this is Princess Grace" or "Don't mention Bing Crosby." Assuming this IS Princess Grace, there wasn't too much room for overlap in their lives: Diana and Charles were married in July of 1981, and Princess Grace died in a car crash the next year. Sadly, Diana herself died in a car crash in 1997.