Ms. Reynolds and Ms. Fisher took their mother-daughter show on the road, performing together in nightclub acts from the time Ms. Fisher was very young, and then performing again, in some version, on “The Oprah Winfrey Show,” in 2011. In a lengthy interview, they spoke of their trials, including a decade-long period in which Ms. Reynolds claimed, dramatically, that they did not speak. “We talked, really badly,” Ms. Fisher clarified. She explained that at the time, she needed to separate — “to forge some kind of character out of … nothing,” she said, her famous wit momentarily leaving her.

In “Postcards from the Edge,” the middle-aged actress is still asking her mother: “Why do you have to completely overshadow me?” But on Oprah, and also in her own life, Ms. Fisher more than held her own, playing a tough, smart-talking princess in “Star Wars”: She, too, was an icon of her time, and she, too, was not quite of this world.

If her mother was forever an ingénue, albeit one who could land a wicked zinger, Ms. Fisher was a blazing comic, a teller of truths with little patience for costume and cover-up. From what she called “nothing,” she forged something big and bold and every bit as brilliant as the woman who raised her, less glittering, more glaring. Mothers and daughters who watched them on Oprah saw a mutuality in their regard for one another, and reconciliation in their rapport. There was humor and acceptance — not so much a fairy-tale ending as a loving truce, bound by devotion.

For the entirety of her childhood, Ms. Fisher had to endure the public’s fascination with her mother, an experience she felt most keenly when they went out in public. “I did not like sharing her,” Ms. Fisher wrote in “Wishful Drinking.” But toward the end of her mother’s life — Ms. Fisher did not know it was toward the end of her own life, as well — she wanted to show the world the person whom she saw, the mother and human, the Oz behind the curtain whom she loved.

That was one reason, Ms. Fisher said, that she consented to having a documentary made about them both, called “Bright Lights: Starring Carrie Fisher and Debbie Reynolds,” which will be broadcast on HBO on Jan. 7. At times, one of the documentary’s directors, Fisher Stevens, was frustrated by just how hard it was to capture the real Ms. Reynolds — sometimes, he told The Washington Post, she asked for her lines, and seemed incapable of dropping a performer’s pretense in front of the camera; one interview concludes with her throwing a kiss, as if she were ending a telethon. Ms. Reynolds, offstage, was a gift she reserved for her daughter and family alone.

On the Oprah special, Ms. Reynolds said of her daughter, “I always feel, as a mother does, that I protect her. Who will do that when I’m gone?” she asked.