She Broke the Barriers Between Royals and Staff
In the past, there has been a distinct divide between royals and their staff. But while Diana reigned, she encouraged her sons to wander about the kitchens and talk with the staff. She emboldened them to help with cooking and cleaning too. William and Harry even played with the staff's children, which until then was unheard of.
She Advocated for Mental Health
Diana never shied away from openly discussing her marital issues with Prince Charles or her struggles with an eating disorder. She was very honest and spoke about her battle with bulimia as "something you inflict upon yourself because your self-esteem is at a low ebb, and you don't think you're worthy or valuable... It's a repetitive pattern which is very self-destructive."