The 69-year-old actress played Sandy’s friend Frenchy in the 1978 film.
Critics of the movie, which also stars John Travolta as the main male protagonist Danny, suggest it is sexist because Sandy feels she must dramatically change her appearance to rekindle her romance with Danny.
Speaking on Good Morning Britain this morning, Conn defended the ending, saying Sandy’s new look was the character “becoming more of herself.”
Conn, who also starred in You Light Up My Life, said: “Frenchy always wanted to be a beautician. She wanted to make people beautiful and bring every great quality in them.
“She failed, she had a few problems in the tinting class over there. She still cared, especially for her friends.
“So when Sandy is all alone by herself after the car race and she decides she wants to be part of the gang, she wants to have fun and allow herself to be emancipated a little bit. She says to Frenchy: ‘Can you help me Frenchy?’ you know.
“So, it’s like the first makeover show, she is becoming more of herself. She is allowing herself to come through.”
The star added: “It’s not so much to get her man but it’s to be who she is 100 per cent. He ran away from the dance because he was dancing with Cha-Cha and she couldn’t confront him because there was this part of herself that wanted to come out.
“It wasn’t about getting him. It was more about being herself."
She added: "Even Olivia Newton-John was seen as a goody good shoes (sic), so she was really excited to liberate herself and bring out this woman, this emerging sexual person.”
During the GMB debate, journalist Olivia Petter said the "problem" with the film was that Sandy is treating to please a man.
She said: "The only reason she does that big transformation is to please a man and that's the problem with the film. That's celebrated at the end of the film.
It's only after she does that that she becomes a socially acceptable person for Danny to date."
Newton-John, 72, has also hit back at claims the musical was sexist in the past.
Speaking about it in an interview with The Guardian, she said: “It’s a movie. It’s a story from the 50s where things were different. Everyone forgets that, at the end, he changes for her, too. There’s nothing deep in there about the #MeToo movement.
“It’s just a girl who loves a guy, and she thinks if she does that, he’ll like her. And he thinks if he does that, she’ll like him. I think that’s pretty real. People do that for each other. It was a fun love story.”