Well, I've watched a LOT of YT broadcasts on YT featuring ex-FBI, LE etc and almost all do not think the kidnap/ransom is real and think 'something else' happened to Ms Guthrie. Add the assertion of AB's source which I really, really (really) did not want to believe and...
Of course for the siblings, they'd want to put their belief in considering kidnap - pay ransom - get her back as it was the most hopeful scenario, until it wasn't... yet still they will pay.
I just think if ransom was real it would have been a lot 'neater' (negotiations) instead of this long, drawn out, going nowhere... although I will acknowledge with technology being what it is today I have NO idea what that would look like (without detection)