You should try to make her feel confident about herself. It is important to tell her that she has a high IQ, therefore she will be able to perform any job she wants. As the IQ is the measure of the ability to reason and solve problems she won't have any trouble dealing with the new tasks she will be in charge of. Another important thing to tell her is that there is always a first time for everything, although she may not be an expert on the new job, she will have the opportunity to learn new things and develop new skills.