Cockatoos are lively, affectionate birds. They are quite cuddly and bond very closely with their owners.
Tame your cockatoo before attempting training. Handle her gently and affectionately every day in a room without distractions.
Choose one person in the house to perform the primary training. If it isn't you, it should be someone who also puts in time and effort to tame your bird.
Refrain from yelling at or punishing your bird. She won't learn any faster; in fact, she'll become afraid of you, and less receptive to training and displays of affection.