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

When a mind is permeated with clinging, subdued by clinging, with a strong will to cling, and that same mind is not experiencing suffering due to that same clinging, there is little you can do to help that mind stop clinging.

When a mind is permeated with clinging, subdued by clinging, with a strong will to cling, and that same mind is experiencing a little suffering due to that same clinging, there is something you can do to help that mind to stop clinging.

When a mind is permeated with clinging, subdued by clinging, with a strong will to cling, and that same mind is experiencing immense suffering due to that same clinging, there is a lot you can do to help that mind to stop clinging.

There comes a time when a mind permeated with clinging, subdued by clinging, with a strong will to cling, is happy in that same clinging: "I'm happy. I have complete control over my son.".

Then, there comes a time, when that same mind starts to experrience a little suffering due to that same clinging and realises: "I have no control over my son. I'm suffering. Who knows the solution to stop my suffering?".

Then, there comes a time, when that same mind starts to experience immense suffering due to that same clinging and realises what is suffering, what are the types of suffering, how are the types of suffering experienced, what is the greatest suffering?

Then, there comes a time, when that same mind, fully aware of its own suffering and fully aware of the suffering of others, comes to realise: "I have no control over my son, but he has a roof over his head. I have no control over my son, but he has food and water. I have no control over my son, but he has ears. I have no control over my son, but he has eyes. I have no control over my son, but he has legs and arms. I have no control over my son, but he is breathing. My suffering is nothing compared to the suffering of others.". By realising this same truth, clinging subsides and wisdom follows: "I have no control over my son. I will never have complete control over my son. Thus, I will control him less.".

The thing is if she keeps on worrying that way, she may end up with not doing at least what is in her control. Tell her the duties of a parent as preached by Lord Buddha in Singalovada Sutta and convince her that she should do or get ready for all of her duties.

1. Not allowing to do evil actions and self destructive actions.
2. Guiding for proper or meritorious and good action.
3. Providing proper education
4. Finding or helping to find a good spouse when the right age comes.
5. Passing on the inheritances.

And she can be a good friend to her own son whenever he needs a good friend, someone who helps him when he is in danger or relieving his fears or sorrow etc.

Further, you can tell her about impermanance, suffering and non self. Nothing is in full control of anyone, that lack of control brings dissatisfaction and there is no one who does not undergo the the first two phenomena. In fact, all mothers have that worry to an extent, every mother cannot take full control of even themselves, so she is not the only mother who faces the issue. When she slowly understands that every mother feels that in different levels, she will slowly get away from that sorrow and fear.

I suppose it largely depends on how close you are to her, or how seriously she would take and act on any advice.

These types of neurotic/anxious behaviors aren't something that are going to disappear by themselves overnight, or by you citing some scriptural passage to her that makes her see the light (most likely, there are cases where people do become enlightened in the scriptures from hearing verse, but in practice this is the exception not the rule).

The most practical way would be for you to, depending on the type of friendship you have, introduce the idea of meditation to her. Spin it in such a way that she is able to see that it doesn't have to in any way be connected with a "religion" or sectarian ideology.

I don't know what your experience with meditation is, but if you have some then you have even more authority it explaining to her that meditating will allow her to see experientially that things are largely uncontrollable, and that all she is doing is creating her own misery in worrying about these uncontrollable things.

Perhaps even convince her to go to a retreat with you, if at all possible :)

Ultimately, you can lead a horse to water, but you can't make it drink. If she isn't ready to hear this, all you'll be doing is blowing hot air into the room. The best way to show others the benefit of meditation is to live your life as an example of the benefits of it.