1953 and 1949
1953:
American actress and singer Marilyn Monroe performed the song in the 1953 film Gentlemen Prefer Blondes
Excerpt:
Tiffany's
Cartier
Black Starr
Frost Gorham
Talk to me Harry Winston
Tell me all about it
There may come a time
When a lass needs a lawyer
But diamonds are a girl's best friend
https://www.youtube.com/watch?v=bfsnebJd-BI
1949:
A jazz song introduced by Carol Channing in the original Broadway production of Gentlemen Prefer Blondes (1949), with music by Jule Styne and lyrics by Leo Robin.
https://en.wikipedia.org/wiki/Diamonds_Are_a_Girl%27s_Best_Friend
Q Drops 1953 and 1949 attached.