This is very interesting - Check out this youtube video (I hope links are allowed here)
at the 15:00 mark. This really clicked for me as probably underlying the motive. I transcribe the message below if you don't want to go through the link.
One of the deleted texts between NK and her friend from August 12, 2018. That's the day before the crime (Sunday afternoon, before her long heart to heart phone calls with CW before SW got home).
"I just feel like I will always be second place like he's been there done that. It's early though we will see. He is very kind to me though."
WHOA!
This is what NK was feeling at the time. There are other messages shown in this video where her and her friend are talking about finding the right one, etc. This is undoubtedly what she conveyed to Chris in their hours-long conversation 2 hours before Shannan got home. It's not a big leap to think he made up his mind to prove to her that it will only be about NK going forward! There are two possibilities for me. We all know NK is a bad liar who obstructed justice here.
But 1. Either she really meant she wanted him to divorce and leave his wife completely and start anew with her, and she was ultimately shocked at what action he took, misinterpreting what she said, or coming to a really bad conclusion about how to address what she wanted, and she pieced together over the next 2 days as FBI started closing in and based on his interactions with her that Yeah, he might have actually harmed his family, wow I'm going to the police now.... After initially conspiring with CW to cover up the relationship in case they search his phone AS PART OF THE EFFORT TO FIND HIS FAMILY
OR 2. She planted this seed and this is what she wanted him to do. And she conspired with CW to delete their conversations to coverup her involvement when she felt like the police were closing in and that he had done a really poor job of covering up his crime and explaining so she knew she could be implicated. And at that point she turned on him when she or they both knew the FBI had him dead to rights. And the plea deal is part of his effort to "protect her."
Either way, I'm pretty sure she planted that seed and this email shows exactly where her feelings were the days surrounding the crimes. This to me is a bombshell.