This year’s Independent Film Festival Boston came to a close Wednesday with a screening of Sundance hit “The Intervention’’ at the Coolidge Corner Theatre, followed by a Q&A with writer-director-actress Clea DuVall and producers Sam Slater and Paul Bernon, of the Massachusetts-based company Burn Later Productions. DuVall got visibly choked up talking about making the relationship comedy, specifically about directing her real-life best friends Melanie Lynskey (who won the Special Jury Award at Sundance for her performance) and Natasha Lyonne. DuVall expressed gratitude throughout the evening for those who supported her feature filmmaking debut, both in-person and in the film’s credits — which highlighted, among many others, DuVall’s “Argo’’ costar and director, Ben Affleck.