Yes even I’m evil I did this cos I wasn’t good enough to look after them is a construction to make her feel better about it. She killed them because she’s evil and she wanted to.I'm firmly of the opinion, and I think @gigilouxx will agree with me, that deep down these narcs do know the truth, but they construct a new truth for themselves and absolutely believe it. So I think she's being 'truthful' when she can't recall/denies everything, but only in respect of her construction of truth, not the objective reality.
Many healthcare serial killers eventually create a narrative of mercy or hating seeing people suffering - generally always comes unstuck because they’ve killed many people that would have gone on to enjoy life and live longer! But it sounds palatable and keeps them in control of the narrative.