Actress/actor turned director Lynn Shelton, whose “Humpday,” “Your Sister’s Sister” and “Laggies” helped define to chatty/semi-improvised subgenre called “mumblecore” by some, has died.

A blood illness, undisclosed, took her at a far-too-young 54. That’s her with “Mumblecore” Godfather Mark Duplass, her “Humpday” (2009) star.

She did a lot of TV (“Mad Men,” “Love,” “GLOW”) and enough indie films to make her mark in her few years as a director.

Her final series was “Little Fires Everywhere,” a Hulu hit just last month.

She collected “Someone to Watch” and John Cassavettes Awards at the Indie Spirits.

She worked with Kiera and Reese and Kerry and Alison Brie and Rosemarie DeWitt and I cannot recall a bad performance in anything she ever directed.

The last film of hers I reviewed (I also watched and reviewed “Little Fires”) was her Marc Maron (her life partner) collaboration, “Sword of Trust” just last summer.

And when I say “classic actress/actor turned director,” I mean somebody who came to Hollywood to work in front of the camera because they knew they were beautiful enough to get casting directors’ attention, who never broke through to stardom but paid attention on sets and used what they learned to move behind the camera.

Go on any set and you see gorgeous men and women location managers, ADs, script supervisors and the like. Ask them their story and it is not unlike Lynn Shelton’s. But she learned the craft and had a fresh take on what dialogue should sound like.

“Mumblecore” was the result — improvised, natural chatter.

She fit that actress-turned-director mold to a T, and helped invent a whole new generational style of dramedy that launched Greta Gerwig and the Duplass Brothers to fame, among others.

Well done.