Nothing is known about Bernadette's life before or after the outbreak started.
Bernadette is one of the still living people in Rozwell, NM. She is the leader of a group who believe in aliens and that they will come to save them.
Bernadette is mentioned (though not by name) by Sarge when she is explaining the great pile, a pileup on the highway. It was created when Bernadette continued to broadcast her message that aliens would take them away from the apocalypse, and people came en-masse, resulting in the pileup.