So, just thinking aloud here and mulling it over but....
From what she's tweeted, it seems her son returned from his Dad's with a new book, and for some reason she went wild over it.
Is it a coincidence that the book is called World's Worst Parents? What I mean is, did she take offence to this, and see it as a dig? If she was already feeling very fragile mentally, perhaps she was triggered in some way by the title. We all get parent guilt sometimes and things can be blown out of proportion when we feel vulnerable.
I don't know, I'm starting to get my usual pity for her and feeling sad that she seems to spend her whole life in a rage, searching for negative things to focus on. I know she's awful, but I feel sad for her again.