speak in front of a large group if people

I would advise my friend to practice in front of a mirror and imagine she is speaking to a groups of people. Because I think the reason that she is afraid is that she is not confident enough. She always wondering weather she had done something wrong. When she is practicing in front of a mirror, she can see the disadvantages and she can try to improve herselfe. With time goes by, she will believe that she will do a good job in front of a large coupe of people.