A person making sure their opinion is heard when no one cares.
In context, the phrase "Diva Number One" must be said in a sassy tone, calling out the diva in question.
If a person is being "Diva Number One," it is your RIGHT to put them in their place.
Mukund: I have to go to the store and buy Puffs Plus with Lotion.
Everyone (in unison): Diva Number One!!!!!