Answer by taking a quote from the following article:

Audra Ann McDonald (born July 3, 1970) is an American actress and singer. Primarily known for her work on the Broadway stage, she has won six Tony Awards, more performance wins than any other actor, and is the only person to win all four acting categories. She has performed in musicals, operas, and dramas such as A Moon for the Misbegotten, 110 in the Shade, Carousel, Ragtime, Master Class and Porgy and Bess. As a classical soprano, she has performed in staged operas with the Houston Grand Opera and the Los Angeles Opera and in concerts with symphony orchestras like the Berlin Philharmonic and New York Philharmonic.

McDonald has also made many television appearances, both musical and dramatic. In 2001, she received her first Emmy Award nomination for Outstanding Supporting Actress in a Miniseries or Movie for the HBO film Wit, starring Emma Thompson and directed by Mike Nichols. She also has appeared on Homicide: Life on the Street (1999), Law & Order: Special Victims Unit (2000), Having Our Say: The Delany Sisters' First 100 Years (1999), the short-lived Mister Sterling (2003), The Bedford Diaries (2006), and Kidnapped (2006-2007), and in the 1999 television remake of Annie as Daddy Warbucks' secretary & soon-to-be wife, Miss Farrell. She sang with the New York Philharmonic in the annual New Year's Eve gala concert on December 31, 2006, featuring music from the movies; it was televised on Live from Lincoln Center by PBS. In 2013, she appeared in the HBO documentary Six by Sondheim.  McDonald appeared as Naomi Bennett in Private Practice, a spinoff of Grey's Anatomy. She replaced Merrin Dungey, who played the role in the series pilot. McDonald left Private Practice at the end of season four, but returned for the series finale at the end of season six to bring closure to Naomi's storyline.  In films, McDonald has appeared in Beauty and the Beast (2017), Ricki and the Flash (2015), Best Thief in the World (2004), It Runs in the Family (2003), Cradle Will Rock (1999), The Object of My Affection (1998), and Seven Servants by Daryush Shokof which was her film acting debut in (1996).  McDonald played Mother Abbess in the 2013 NBC live television production of The Sound of Music Live!.  Since 2012, McDonald has served as host for the PBS series Live From Lincoln Center, for which she shared an Emmy Award for Outstanding Special Class Program with the show's producers. On August 1, 2017, it was announced that she had been added to the main cast for the second season of The Good Fight, reprising her role as Liz Lawrence from The Good Wife season 4.

What was her role in the season finale?
returned for the series finale at the end of season six to bring closure to Naomi's storyline.