She has frequently worked with American independent film directors Steven Soderbergh (Schizopolis, The Limey, Full Frontal) and Sofia Coppola (Lost in Translation, Marie Antoinette, Somewhere, The Bling Ring, The Beguiled and On the Rocks).
Flack's work on Lost in Translation won her the BAFTA Award for Best Editing.
She won a Primetime Emmy Award and an American Cinema Editors Eddie award with Robert Pulcini for co-editing the HBO film Cinema Verite.
Flack began her career working as a production assistant on the film Kafka where she first met film director Steven Soderbergh.
After assistant editing on a handful of other independent films, Flack was hired by Soderbergh to edit his self-financed experimental film, Schizopolis.