This is an old field song. They are singing "she lie" not sea lion. It is possible to imagine all kinds of back stories but I imagine a young white woman who had been a childhood friend of the writers of the song and as she grew to drink coffee and tea she began to distance herself from her former playmates who were now slave field workers. She began to lie, she lie.
The rooster crows as it did when Peter denied Jesus and as "she" denies her former friends.