How to talk to a friend about "lack of control" in what happens to her son?

I know a friend, who doesn't practice buddhism, and who is always worried about her young son. She is always concerned about everything that could go wrong, or things which could happen out of her control that she can do nothing about. I've always been one who doesn't worry about the things that are out of my control, but I don't think that simple piece of advice is enough for her to act on it. I'm sure it's something that is "easier said than done". What advice can be found in buddhism for this situation?