I agree that she was a triple threat and one of the greatest.
She could sing and had such a mature voice at a young age.
She could act. Watch her monologue in "A Star is Born" where they never take the camera off of her. You can still watch that scene today more than 50 years later, and it is still one of the most honest pieces of acting on screen.
She could dance. Catch her in Easter Parade. Not many women had the guts to get up next to Fred Astaire.
I had read somewhere that it was Shirley Temple's mother that didn't want her to do The Wizard of Oz. (Maybe in Shirley's autobio?)
Over the Rainbow was almost cut from the movie because the running time was too long.
Shelley Winters talks in one of her autobios about going to a party and someone said something nasty to Judy. Later Shelley went outside and Judy was sitting there crying. She did have a very fragile self-esteem.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.