arm candy
n. An extremely beautiful person who accompanies a member of the opposite sex to a party or event, but is not romantically involved with that person.
That's garbage," says Jenny, who is 44, and has been married to Ricky, aged 32, for four years. "It is so insulting to suggest that I chose Ricky as a trophy husband, as something I could afford, and which demonstrates how free and successful I am. When Ricky and I started going out, I was forever sensing people thinking 'look at her with her flash job and her flash car and that handsome boy', and it's true, a number of people did think that he was arm candy. But in fact he's the love of my life.
—Louisa Young, “Don't mind the gap,” The Guardian (London), June 11, 1999
Now that gossip and society columnists are popularizing the phrase "arm candy" to refer to an attractive young thing who is escorted by an older, more powerful person for others to eye appreciatively, how long will it be before they begin using a companion term, 'room candy,' for a similarly attractive young thing who is invited to receptions or parties for decorative purposes?
—Stuart Elliot, “Twenty, count 'em, 20 questions on media and marketing to astound and amaze your friends,” The New York Times, November 30, 1998
1992 (earliest)
All About Eve (1950, FoxVideo). [Marilyn Montroe had] already had mini-roles in eight movies when she turned up as George Sanders' arm candy in the party scenes of this film. But her jewel of a performance as an actress-on-the-make caught the public's attention.
—Marcia Froelke Coburn, “Marilyn's enduring appeal,” Chicago Tribune, August 21, 1992