This is actually one thing that's nagging at me (other than the absence of facts, but that will improve).
I cannot see a motive I would believe.
Of course, not all crimes make sense. Therefore it's also annoying to me as I work in mental health, that I cannot see a mental health background I would think as more likely than the others. And my theories vary wildly (from something Munchausen-like to just being depressed and being bad with social stuff, from experiencing psychotic symptoms to being a domestic abuse victim).
What would be the reason for EP to (try to) kill DP, GP, HW & IW? What would EP gain from killing them?
Please do not lynch me - I am not saying she must be innocent. She might be guilty, it is not unlikely. But I just cannot piece it together and it is not something I feel too often in these stories.
I feel like her original plan was to get rid of her husband. Probable motives would be child custody and division of assets and perhaps some anger/resentment, which is often present when couples separate.
At the time of the luncheon date, EP appeared to have full custody of the 2 children and she seemed to be in control of the real estate holdings. [which were purchased with her inheritance]
However, the divorce has not been finalised. It was a critical time for her to try and preserve her hold on the property and the children. Reportedly the luncheon was designed to be a mediation of some sort concerning the couples separation.
That brings the 4 victims into the middle of the divorce issues. In my opinion, they were trying to leverage some kind of influence in SP's favour----maybe more custody time with the kids and a more beneficial property settlement?
And that doesn't even open the can of worms concerning religion. EP claims to be a proud Atheist while her ex and his family were devoutly religious. Were they pressuring her to send the kids to church or to a religious school, or to spend more time with them in the future? Were they judgmental about how she was as a mother?
I can see a scenario where EP just wanted to be rid of those people that she thought were trying to wrestle control of her children and her inheritance. Maybe she wanted to be free and clear to move where she wanted and do what she wanted with her new single life---without interference.
Her original target was probably her ex, and she saw an opportunity to take out his family at the same time, when the luncheon meeting was planned. After she had already planned her toxic menu and began cooking, she got the cancellation from SP. She had a big decision to make. Should she continue with the toxic menu if he was not going to be there?
I am kind of surprised that she did. Which makes me think that maybe much of the motive was anger/resentment and rage. JMO