Thanks for this.
This might make me look like I'm talking about everybody, but I'm actually notorious in my job for being somebody who avoids conflict. If people start talking about other people, I remove myself from the situation. I also don't openly swear in the way EP did.
However, in every workplace, friendship group, family dynamics I've ever been in there have been many many people talking negatively about others behind their back. This is even people they like and are friends with.
The Facebook messages I saw were a bit crasser than you're average but I thought represented a potentially understandable family frustration. Saying she was done with the family, is the sort of hyperbolic thing people say all the time when they're upset.
They absolutely did demonstrate two different sides of their relationship (and an obvious lack of real religious faith), but again I can relate somewhat. My in-laws are the sort of people you couldn't have an open disagreement with and often because of religion.
They could be a motive for murder, I'm not saying that, and if she is guilty there has to be one that isn't strikingly obvious. I'm arguing that if I was a juror, and I was talking about reasonable doubt etc, I wouldn't think it was a very persuasive motive.
Of course the prosecution don't need to prove a motive, but I think it's naive to think it won't be a consideration when looking at reasonable doubt.