I have thought for some time Wendy was the primary driver. And the ex boyfriend's police interview confirmed it for me. Not a nice person, plays the victim. Wendy got what she wanted, and her family were turned into tools. And she covered her tracks pretty good except for visiting the crime scene!RE - "dismissed with prejudice." In other words the judge had ruled this was the end of the matter, there would be no further hearings regarding relocation. WA was cognisant of this, yet she did not inform her mother of this when the hearing was completed (DA was outside in the waiting room).
In fact she never informed DA or HA of this ever and allowed them to carry on thinking she still potentially could be granted relocation rights at a further hearing. Which was not true. This resulted in DA sending more and more vitriolic emails, regarding relocation as well as her thoughts on Dan, which were becoming increasingly more venomous.
So as a few people have pointed out, perhaps WA was, ultimately, the mastermind. She painted out Dan to be this abusive monster, lied about his behaviour and lied about the relocation. This fostered a deep hatred amongst her family for Dan and perhaps was the catalyst for them to plot the murder which WA all too willingly agreed to.
So I find all her mannerisms turning her head back and forth "innocently", soft voice and eyes...all acting. Like Donna told her, she knows how to act.