Burkhardt first hit the small screen in 1997, when she competed in the Miss Teen USA pageant as Miss Maryland Teen USA. The National Pageant was won by Shelly Moore of Tennessee. She later moved to New York to attend New York University, where she won the Miss Manhattan pageant, the Miss New York pageant and competed for Miss America 2000. Burkhardt performed vocal talent at that pageant, singing "Take Me As I Am", which she would later record as Emma on the concept album for the film and national tour concert version of Jekyll & Hyde, Jekyll & Hyde: Resurrection.
Burkhardt's first major credit was the Jekyll and Hyde: Resurrection Tour, in the starring role of Emma Carew. This version of Jekyll and Hyde was told in concert form. A new song, "If You Only Knew", was written for her by Leslie Bricusse and Frank Wildhorn. Her Broadway debut came when she was cast as Lucie Manette in the Broadway musical adaptation of A Tale of Two Cities, which opened for previews on August 19, 2008 at the Al Hirschfeld Theatre in New York and had an official opening of September 18, 2008. She was persuaded to audition for the show by star James Barbour, who was at a dinner meeting with her. The production announced on November 4 that it would be closing on November 16, but the producers announced on November 7 that due to poor ticket sales the following week, the production would close on November 9, 2008. She then played Sophie Sheridan in the Broadway production of Mamma Mia. She began her run on January 27, 2009 replacing Allison Case. Burkhardt played her final performance on September 20, 2009 and was succeeded by Alyse Alan Louis.
Burkhardt has been attached to several other projects. Most prominently, she was connected to Wonderland: Alice's New Musical Adventure by Frank Wildhorn. Singing the role on several demo recordings, she also premiered the song "Once More I Can See" at the Graz Theatre Festival as part of the "Frank Wildhorn & Friends" series, this role was originally developed for her. The show made its world premiere on December 5 in Tampa, Florida starring Janet Dacal. However, her voice was heard on several advertisements for the Tampa premiere including radio and TV spots. She was also a part of the workshops and demos for Rudolf - the Last Kiss as Mary Vetsera, and performed the role of Mercedes in The Count of Monte Cristo recordings, earning a double platinum record for its European Release and workshops (opposite James Barbour, her co-star in Tale). Both of these shows have seen large success in Europe.
In addition, Brandi was attached to Bonnie & Clyde, having done readings of this as well, and also concept recordings of music from Don Black and Frank Wildhorn. The musical "Mary Shelley's Frankenstein" was written specifically for her, though the show has not had an official performance or recording yet. It is unknown the status of the project or if Burkhardt will star.