In the musical Showboat, why does Magnolia choose to sing the song "Can't Help Lovin' Dat Man" in her audition to get the job at the night club?

Magnolia, at
the beginning of the musical, is a rather naive teenager whose dream is to become an actress on
the stage, such as the leading ladies she watches on her father's show boat. Magnolia is friends
with Julie, the leading lady for the current show on the Cotton Blossom, and looks up to her
every move...