Harper Lee and Mary Badham

American novelist Nelle Harper Lee died in her sleep on Friday. She was 89.

Lee wrote only one book, the modern literary classic To Kill a Mockingbird. She never wrote another.

Mary Badham was 10 years old when she met Ms. Lee on the set of the 1962 movie, To Kill a Mockingbird. Badham starred as tomboy Scout Finch. Like Lee, Scout was the daughter of a respected attorney who was committed fighting to racial injustice. They remained friends for 50 years.

“She was a dear friend,” said Badham in an exclusive interview with The NY Daily News.

An emotional Badham recalled her favorite memories of Lee: “The last few times of being together, when we were just laughing and talking,” she said.

To Kill a Mockingbird was published in 1060, 3 years after Lee turned in a manuscript with a different title, Go Set a Watchman.

The publishers — the now-defunct J. B. Lippincott Company, made her rewrite the manuscript over and over until, out of frustration, she flung the pages out a window into the snow.

She called her literary agent in tears. Her agent, Tay Hohoff, told her to march outside immediately and pick up every page.

“I was a first-time writer, so I did as I was told,” Lee said in 2015.

After 3 years of setbacks, Ms. Lee reshaped Go Set a Watchman into Mockingbird, a novel worthy of publishing. But she didn’t have high hopes.

“I never expected any sort of success with Mockingbird. I was hoping for a quick and merciful death at the hands of the reviewers but, at the same time, I sort of hoped someone would like it enough to give me encouragement,” she told Roy Newquist in a rare interview in 1964.

To Kill a Mockingbird was an immediate bestseller, racking up awards and accolades including a Pulitzer prize.

Of the Oscar award-winning film adaptation of To Kill a Mockingbird, Horton Foote said: “I think it is one of the best translations of a book to film ever made.”