That's according to James Corden, , who went on to call his Into the Woods co-star "the worst" at a Hollywood bash.
Of course, the British chat show host was only joking as he presented Streep with a distinguished collaborator prize at the Costume Designers Guild Awards.
Oscar favourite La La Land and Marvel's Doctor Strange were among the films honoured at the Los Angeles event.
Corden was referring to Streep's spat with US president Donald Trump when he made his jokey remarks.
He claimed the first time he introduced himself to Streep, at a London restaurant, she mistook him for a waiter, saying: "I'll have the lemon-crusted salmon and a Diet Coke with no ice."
The Late Late Show host joked: "What I'm trying to say is, and it's time that someone said it, she's a complete bitch. She is the worst.
"Now listen, I disagree with almost everything Donald Trump has ever said but when he tweeted that... I'm joking, xvvry4347, of course. It's great to see someone like Meryl finally recognised with an award."
Streep - who starred as a fashion magazine editor in The Devil Wears Prada - was recognised for her "unwavering support of costume design and creative partnerships with costume designers".
Accepting the accolade, the three-time Oscar winner paid tribute to the "artistry" of the "many wonderful designers" she had worked with over the course of her long career.
She did not mention Mr Trump as she collected her award, but said she had wanted to be a costume designer herself.
"I have to dedicate this because it means a lot to me, ," she said. "Not because I wanted to be a costume designer - which I did - but because my mother really wanted to be a costume designer.
"Halloween was like the run-up to fashion week in my house."