Actually, I am a mother and grandmother via my DD. I do not hate mothers; I am aggrevated by women and men who have children without planning for the possible consequences and come whining to the forum.That is a massive stretch and you are saying it only to scare this mother because you seem to hate all mothers.
They need to know the worst possible scenario and go forward only if they are prepared to deal with it. In this case OP had a child with a guest worker; obtaining a GC via employment is not a sure thing and is dependent on the employer and available USCs and LPRs qualified and desiring the position. The child could be a dual citizen with a male dominated country/culture. There is certainly the possibility that the child would not be returned to the US even if it is unlikely.
Giving her a view through rose colored glasses does her a disservice. She is also ridiculous to expect that she will be supported by his employment elsewhere as she has been in the past.
She also should have been aware that his earning potential outside the US is far less than here. Even in countries with living standards similar to the US may have salaries far lower than here in the US. (DS took a position outside the US for 2/3 his US salary because he likes where he lives there more than what is available with his company in the US and he gets better benefits and has a lower cost of living.)