MusicalEndorphins Admirably helpful post there, really, but you are making a fundamental mistake here... you applied logic, common sense and normalness to someone who is not in possession of any of them.
What G2B needs is to fail to react to anything.
Giving the links, researching bits and bobs, making suggestions is getting sucked right back in again.
G2B, you mother has adopted the hair shirt technique.
If she wants to be in a crappier bedroom - her choice.
If she chooses to not put the electric blanket on when she's always done it before - her choice
a sudden inability to carry 6 cartons of milk when she managed PERFECTLY well only a week or 2 ago - her choice
Washing/ironing/walking/talking whatever - her choice
I agree that you have the strongly worded 'STOP the whining/tears' conversation with her, as it's just pathetic. she has NO business guilt tripping ANY of you. You need to go in hard on this and state that you will only pop in when YOU need to, and without the kids if she is unable to behave herself in a proper sane adult manner.
Don't forget: HER behaviour made sharing a house IMPOSSIBLE. Her undermining of you, your DH, her manipulation of YOUR DS, her ignoring your DD, her pick and mix approach to coping or not coping, her emails full of shite to your DB, all of that. She wanted to rip your marriage to pieces, to have your H leave you all so that she could get you as her dogs body all to herself.
SHE did this.
She won't accept this, ever, as for someone to behave like that, to be this nasty would mean that SHE is nasty, wrong and that she is reaping what she has sown.
From the sounds of it, she has never taken responsibility for ANYTHING, not her words, deeds, actions, mistakes out and out WRONGS.
Why would she start now? seriously?
If you expect that she will always be this way, that nothing will ever change, that you will ALWAYS be the one in the wrong in her eyes, then you will be able to detach, move on from this, heal and perhaps even have a fairly OK relationship with her, as you will be managing your expectations and only asking/expecting what she is capable of doing.
If you are expecting her to one day wake up and be nice, to learn from all this, to be the mother you so deserved, you are going to be bitterly disappointed.