One more thing... Instead it feels like the end of the arc tells us "Well, she's NOT a member of this nuclear family..."
I hear you, but I didn't read "Well, she's NOT a member of this nuclear family..." as a purposeful message. Personally, I think it's just sloppy writing. There was nothing in that arc that was well-done or sophisticated. I don't think that after all the mess we saw before, the writer could jump in with as sophisticated a concept as *that* at that point. I think it was just a ham-handed attempt to gimmick up a story with a reward reveal at the end.
Could certainly be wrong, but I'm judging by the writing that went before that big finale.