EXCLUSIVE:  still has fond memories of her beloved co-star .

The pair worked together in 1944’s “Meet Me in St. Louis,” a musical that told the tale of a turn-of-the-century family. The film was directed by , who would become Garland’s second husband in 1945. The pair called it quits in 1951.

“I loved making that movie,” O’Brien told Fox News. “I almost didn’t make it because I was under contract to make other movies for MGM. And of course, [MGM co-founder Louis B.] Mayer did not want to pay you much! It was a very small salary. But my mother thought, ‘Her pictures are making money. I gotta protect my child.’”

“My mother went into Mr. Mayer’s office and said, ‘I want $5,000 for my daughter,’” the 84-year-old continued. “That’s what MGM’s top stars were earning a week and my films were very successful. My mother wanted to make sure that was in my contract. Of course, he cried. He could cry better than I could when you asked for money!”

American actors (left to right) Tom Drake (1918 - 1982), Judy Garland (1922 - 1969) and Margaret O'Brien in a promotional portrait for 'Meet Me In St. Louis', directed by Vincente Minnelli, 1944.

American actors (left to right) Tom Drake (1918 – 1982), Judy Garland (1922 – 1969) and Margaret O’Brien in a promotional portrait for ‘Meet Me In St. Louis’, directed by Vincente Minnelli, 1944. (Photo by Silver Screen Collection/Getty Images)

“So of course he said, ‘This is terrible, we can’t possibly do that,’” the former ‘40s child star recalled. “My mother then said, ‘Well, if that’s the case, we’re going on vacation.’ And that’s what they did. We headed off to New York City. Meanwhile, they already had another little girl put under contract. They already had her rehearsed and fitted for costumes. That little girl was already told she was going to do the movie.”

According to O’Brien, it wasn’t uncommon for the studio to have a lookalike actor or actress on hand in case one of their stars became problematic. 

“It was their way of saying, ‘You better behave because you’re replaceable,’” said O’Brien.

However, Mayer soon realized that he couldn’t pass up the chance to have one of the most sought-after child stars appear in the film, which would mean cashing in at the box office. He gave in and O’Brien was offered $5,000 a week.

Actresses Margaret O'Brien and Judy Garland dancing with hats and canes, in a scene from the movie 'Meet Me in St Louis', 1944.

Actresses Margaret O’Brien and Judy Garland dancing with hats and canes, in a scene from the movie ‘Meet Me in St Louis’, 1944. (Photo by Archive Photos/Moviepix/Getty Images)

“It almost ruin that little girl’s family with disappointment, which was a terrible thing for the studio to do at that time,” said O’Brien. “But I went on to do ‘Meet Me in St.’ Louis’ and I loved making that movie. We were very much a family. We all got along and enjoyed working with each other. And I think that’s what made the film such a classic. It was about a Victorian family that was very close. And in real life, we actually were just as close, too.”

O’Brien said she instantly connected with Garland on set.

“Oh, she was so wonderful!” O’Brien gushed. “She really was. She was just wonderful with children. She was childlike herself. She loved to jump rope on set with the other children. She always was making me laugh. I just loved her.”

In the film, Garland’s character Esther Smith is known for singing “Have Yourself a Merry Little Christmas” to her brokenhearted sister Tootie (O’Brien). The family was gearing up to leave behind their beloved St. Louis home for New York.

Judy Garland originally didn't want to sing 'Have Yourself a Merry Little Christmas' to Margaret O'Brien because she thought the lyrics were too depressing.

Judy Garland originally didn’t want to sing ‘Have Yourself a Merry Little Christmas’ to Margaret O’Brien because she thought the lyrics were too depressing. (Getty Images)

However, O’Brien said Garland initially refused to sing the song, which continues to be a holiday favorite decades later.

“The original lyrics were very dark and drab, which I guess fit the scene because we were supposed to be sad,” said O’Brien. “But Judy said, ‘I can’t sing this to little Margaret! She’ll cry and everyone will think I’m a monster!”

Film producers refused Garland’s request to revise the lyrics, reported. According to the outlet, it was co-star Tom Drake who took songwriter Hugh Martin aside and encouraged him to make the change. Martin later said he went home and wrote a more hopeful version of the song that was used in the film. The track would go on to resonate with American troops serving overseas during World War II. Garland later sang it live at the Hollywood Canteen, a club for servicemen.

“Thank goodness they lightened up those lyrics,” said O’Brien. “Of course that’s what made it such a classic song. It’s still heard every year during the holidays. And we can thank Judy for that.”

Margaret O'Brien (left) told Fox News she still has wonderful memories working with Judy Garland (right).

Margaret O’Brien (left) told Fox News she still has wonderful memories working with Judy Garland (right). (Bettmann Archive/Getty Images)

O’Brien said that “Meet Me in St. Louis” held a special place in Garland’s heart.

“There was a romance with Vicente Minelli,” she said. “And from their romance came Liza Minnelli. So of course, the film held wonderful memories for Judy. Vincente was a very kind director who was easy to work with. He made sure that the studio didn’t overwork Judy and that she had reasonable hours.”

“Unfortunately, other directors overworked Judy,” she shared. “But he protected her. And he made sure that we had a happy, calm set with good hours. And he made sure Judy got plenty of rest. She was always very happy on set. I never saw her sad or nervous or anything like that while filming. It was a positive experience for all of us.”

O’Brien said she and Garland kept in touch over the years. The icon passed away in 1969 at age 47. Her cause of death was ruled as an accidental overdose of barbiturates.

Margaret O'Brien (right) said she still keeps in touch with Judy Garland's children.

Margaret O’Brien (right) said she still keeps in touch with Judy Garland’s children. (Photo by Donaldson Collection/Getty Images)

“The last time I spoke to her was at a big Hollywood dinner,” said O’Brien. “She saw me, came over and said, ‘Oh, hello Margaret! How are you?’ Every time we saw each other, it’s as if we hadn’t been apart. I’m now very good friends with her children, especially her son. They all turned out to be very sweet, wonderful people. You can just tell how much those children love their mother. I certainly loved her and I just worked with her. She was a truly special person. And I never forgot her.”