Okay, that's it. After listening to that interview, reading what the grandfather said, and with all the other info from the Smiths, I'm at 100%. She killed him.
I'm not an expert, but MOO is that she's most definitely personality disordered, most probably sociopathic, and I think she may be having a psychotic episode or close to it.
I say psychotic because whereas she's not having hallucinations or delusions such as aliens or demons after her (or not admitting to them), and she is oriented to reality in terms of knowing where is physically (she knows she's in jail, she knows she's been talking to the FBI, she recognizes Tammi, she remembers her dealings with Tammi), she is not connected to reality in terms of recognizing the gravity of her situation, or the gravity of the implications for Gabriel.
It could maybe not be psychosis at all, but just sociopathy, i.e., she doesn't see anything wrong with what she did, and doesn't care about Gabriel therefore doesn't even think about the gravity for him.
Actually, now that I've typed this LOL I'm going with sociopathy. It's hard for me to say psychotic when someone isn't hallucinating or having delusions such as demons or aliens or thinking they're the Pope. *Could* still be a psychotic break, but this one definitely will take a psychiatrist to determine.