Which figure of speech is used in this text?
Dear Ella
Our Special First Lady of Song
You gave your best for so long
This is true.
—Dee Dee Bridgewater, "Dear Ella"

 - oxymoron
 - apostrophe
The text uses apostrophe, a direct address to an absent person or a nonhuman entity.
Dear Ella is a direct address to Ella Fitzgerald, who died in 1996.