What is the expiation for a girl taking money from her father without his knowledge, and is it by informing him and asking for forgiveness or by returning the money?

The expiation for the sin is through repentance to Allah and returning the money taken from the father without his knowledge, or seeking his forgiveness for it. If the father forgives her, there is nothing upon the questioner. If he does not agree to forgive, then she must return the money according to her ability.