What strikes me is that Lady L was very barmy but she was also very abused. How unreliable is she, really, is what I want to know.
In the 60s and 70s the dope they gave people with depression was very full-on, and that as much as anything would have made her an unreliable witness.
Lady L was repeatedly undermined by her husband who toured Chelsea' various private doctors begging them to section her - ie he could get the house and the money. In the end, though, even the private docs, who were part of his friendship circle, refused and warned her.
Lady L was treated at the Priory, which is well known in rarified circles as being fucking useless. I have a friend whose dad was in there after he was beaten up/head injury at the same time as Lady L - he stayed 3 years, smacked out of what remained of his skull, and only got better when they let him out.
Regardless, she might be nuts, but she's not stupid and she doesn't sound like a liar. The motive she gave Lord L - that killing her meant he saved money - makes perfect, indeed the only, sense. What she said about her DH freaking when he saw she'd fled makes sense of the rest of his flight.
What gets me most is the way her relations defended him. No wonder she was peculiar and went for abusers.
She is a bad mother. In her defence, the upper classes aren't great at that, and she was very, very frightened and ill. She has a chilling coldness, even now, but she's lived a bloody odd life. The children were definitely better off without her, and I'm not afraid to say under the circs there's no shame in that.