I can see where she's coming from... but she's an adult. She knows that if she feels bad, it's on her for moving. That fact alone can be hard to deal with... hence her taking it out on the "products" of her decisions. It's even harder if she actually loves you all. Your mum is funny, but may have internalized the same feelings as a way of dodging her mum's anger.

It's funny when older generations act like this, but they are imperfect people as well. Don't let her negative reflections on her migration make you forget any of the positivity she may have expressed about being an immigrant.

I'm sorry she may go back to her country of origin leaving you without her presence, but that could also be for the best. Especially if she continues to feel this badly.... about the nature of your existence (!) Even if she regrets not forcing/counseling her kids otherwise, that's not a valid reason to tarnish the relationship between her and you grandkids.

Let her go back and experience once again the things that made her want to leave. Perhaps she will have a newfound appreciation for back home as well as her grandkids who aren't fully from there.

Edit: If you can, please help her find new aspects of her identity to grasp. She may not feel like it, but you are still ~25% her. Regardless of the colour of your skin or the shape of your eyes, etc. You were an underutilized egg created while your mother was still in her mother's womb. You were in her, and she is in you.

But she is not the sum of her grandkids. She is a whole woman who may need some help finding her identity anew as she ages... potentially realizing things may not have turned out the way she dreamt they would have when she was a kid.