It's not like she doesn't like the taste of the bread. She won't even try it! She just picks it up and slings it out of the bowl. I don't think she has ever had anything but seeds to eat (she is a rescue) and she doesn't recognize anything else as food. She won't even try corn

All my birds like corn,even my finicky cockatiels. I just keep offering it to her every day and she keeps throwing it to the bottom of the cage.