The girl in the red dress in the film is different to the girl in the red dress
The Girl In Red in real life was Roma Ligocka, who survived the holocaust and wrote The Girl in the Red Coat.
She has stated that Schindler's List was the inspiration for her book, as she saw the little girl in red in the film and was reminded of herself. To quote from her:
"When I saw the film it was like a flash of lightening," she
explained. "All of a sudden fragments, bits and pieces from my past,
grew together to become one."
"I knew at the age of two that I was not supposed to live, that I
would be killed sooner or later," she recalled.
"I wanted to live so badly and my only thought was that I needed to
The Girl in Red in the film was probably a fictional character (although it could have been a retelling of her story, though that seems unlikely), whose red coat was the only flash of colour in the film. To quote from the Wiki (which references Steven Spielberg: A Retrospective:
Spielberg said the scene was intended to symbolise how members of the
highest levels of government in the United States knew the Holocaust
was occurring, yet did nothing to stop it.
"It was as obvious as a
little girl wearing a red coat, walking down the street, and yet
nothing was done to bomb the German rail lines. Nothing was being done
to slow down ... the annihilation of European Jewry," he said. "So
that was my message in letting that scene be in color."
Incidentally, the actress who portrayed the fictional girl in red, Olivia Dabrowska, was traumatised for years after the film, when she broke a promise to Spielberg and watched the film when she was 11 (he wanted her to wait until she was 18).