I think what I was originally wondering is whether we have gotten Morrigan wrong or Flemeth wrong. Was she really that terrible of a mother? Or was it that, yes, she was a terrible mother, but only because she is a goddess and needed to prepare Morrigan for becoming a goddess. Goddess first, who cares about mothering? Urgh... well, that certainly fits in with NPD right there.
A little of both I think. What I got from Mythal/Flemeth is she very much has a dual nature...maybe that comes from Mythal being merged with Flemeth, who was once mortal, or being consort to Elgar'nan...or maybe because all spirits/gods have a dual nature to them. She is a protector and represents justice, but her help comes at a cost (always has a catch) and she also represents vengeance. She represents nature and rebirth, so therefore she must also represent death--nurturing but vengeful.
Morrigan misunderstands her intentions and thinks she wants to steal her body as a hostile takeover, but I don't believe Flemeth sees it that way. She seems genuinely hurt when Morri calls her a bad mother. I also find it interesting how Morri is surprised (and somewhat appalled) Flemeth would consider possessing a male, when she finds out Flemeth wants her son.
I like Morrigan's character development a lot, in the world state where she has Kieran. She seems bound and determined to be a different sort of mother, which fits nicely with the theme of Morrigan representing the new goddess/mother figure for the new age. She has some different and new ideas on how to approach the world.
Has anyone seen American Horror Story, the 3rd season "Coven"? Reminds me a bit of the relationship between Cordelia and Fiona.