I have always thought Diana’s vocal style lends itself well to the duet, particularly ballads.
Which songs that Diana has recorded over the years do fans think might have made for great team work. Some of mine are...

”In Your Arms” with Will Downing
”Experience” or “I Love [[Being In Love) with Barry Gibb
”Best Years” and/or “Let’s Make Every Moment Count” with Luther Vandross
”Cross My Heart” with Lionel Ritchie
“Hard For Me To Say” with Luther Vandross
“Shine” with Mick Hucknall
”I Love You” with Smokey Robinson”