She gave birth on Saturday.
Black Widow is set to be released in November after it was delayed because of coronavirus.
Whether it was an experimental fuchsia design or a ballerina-inspired dress, pink was the colour of choice for the night.
The actress and singer said there was concern she would be seen as 'over'.
The regal drama also stars Joel Edgerton, Robert Pattinson and Lily-Rose Depp.
The star of Flack is concerned about online habits.