Thnaks Ozmanic,
She applied for her 457 visa by herself and it has been approved (She was lucky that she tried to include evryone in the application but due to the system error it didn't happen !). Once her 457 granted, she submitted the application for her Husband, son and daughter. Then DIBP asked about this letter and eventually, case officer asked to withdraw her son's application. She still got approved her Husband's and daughter's 457 and they are here in Australia with her. Now she is planning to apply for PR for herself , her husband and daughter and once they get their PR planning to conatct Immigration agents and apply for her Sons PR with their advise. Hope it is the right way to do?