The 49-year-old actress feels like the documentary has offered her her "first real starring 'role''', although she worried her candid look at her illness might have "horrified" her mother.
She told Vanity Fair magazine: "Honestly, [this is] my first real starring 'role'. "My beloved mother would be horrified how I let myself go in front of the camera. 'Abhorrent!' she would say."
Blair hopes the documentary will be informative and offer hope to people. She said: "I had the conviction of thinking I had something to share.
"You keep opening windows or closing doors and finding tools. I hope my little life gives someone who needs it some hope or a laugh or more awareness of ourselves. I hope the film shows that MS varies. That people's strengths and weaknesses vary.
"All the emotions of life make healing variable too. For all of us."
Director Rachel Fleit - who also has an autoimmune condition - thinks the documentary shows just how much of a "star" Selma is.
She said: "She has felt like a supporting actress. But she becomes a leading lady. She finds a whole new purpose in her life; she fully embraces herself. Now she inspires millions. She has an enormous platform on social media …
"We see it [in the film] so clearly—she's just such a star."
