The multi-faceted career of the great Garland would be tough enough to imagine as an actress, but to go out an DO what Davis did to this characterization, almost defies the word, "talent". She IS Judy Garland, in every scene throughout the film.
She shows you the person inside the "star", and the studio-created nova that had audiences screaming for more and more. She strove to give them that, and she paid for it dearly, with personal anguish and a reliance on drugs that eventually killed her. She became the "property" of the public and while in her earlier years, she enjoyed that acclaim, it ate her up later in her movie life.
If you knew ANYTHING at all about Judy Garland, you MUST watch this tour-de-force by the amazing Judy Davis. As I pointed out in the heading, in this film, they are one and the same.