OP, please re read the above.
I ( as a mother) really can't understand her moving abroad when you were 19 (if she had any say in it, and if she didn't, then that opens a whole new can of worms) but she is back now and seems to be trying to open the lines of communication, albeit somewhat clumsily.
As well as being Mothers, we are also people and people are different. We are shaped by our own life experiences.
You seem entrenched in blaming her because (in your mind) she rationalised/excused the move by saying she would be closer to her sister. Therefore, if she had a choice, she was choosing her sister over you. Is that how you feel?
Cast your mind back to when you were at University, would you have visited home very often, called weekly etc, etc? I suspect not, but, I also suspect, you will say that you would, had they been available. Is that really true? At 19, you were old enough to go away to university and do your own thing.
I think many children expect their parents to be there in the background but not bother them, until it suits them. Many parents don't just want that and see the empty nest as a time for themselves. Life is short. Parenthood is a balancing act and not all of us get it right, but we try.
I think you need to draw a line under this very damaging past and move forward, as you have done with your Dad. Or, if you can't do that, sit her down and really tell her how you felt and ask her how you can both get past it. None of this she doesn't like to talk about it is getting you very far. If you need to talk about it, then insist on her listening.
Going forward you should remember that no one is perfect and that having children is very hard. We all do the best we can with the tools we have at our disposal.
Suppose your children held the divorce against you for whatever reason? You could justify it, but they may not understand it and they may then hold you to account as you now hold your mother to account. Would you want that to go on for years?
Lower your (unreasonable) expectations and get rid of your air of superiority for being a career woman as opposed to a sahm.
This is a valid choice and to denigrate that choice is not very feminist. Both choices are equally valid.
Try to engage with her on her level and you might be surprised at how things will change. Talk about the weather, the grandchildren, the news, and in time, deeper conversations will occur more naturally. Or maybe they won't, seek them elsewhere if that is the case.
I use the mantra with my 4 children 'Parents are people too' and with good will on both sides and with (in our case) wonderful DIL's, we all get on really well. Respect is key.
You can apportion blame or you can move past it. Only you can decide which way you want to proceed. Good luck OP.