I'm popping in and out of this thread as it's moving insanely fast and impossible to keep up for slow pokes like me!
I'm veering on the side of a long stewing grudge possibly personal or acquaintance/someone known to her. I can't see it being anything else after I review it all.
I don't believe there is an actual ransom note was there? It's dragged on too long for that in my opinion.
I don't think it's familial/insurance/inheritance related as there's 50 million other ways (well not literally but YKWIM) to have someone 'pass away' to get insurance.
Taking a possible living, fighting, immobile senior is not the way to get rid of someone for insurance motives MOO.. So that leaves a grudge of some sorts for me. Or did she stumble on some info? Fraud or embezzling of funds from somewhere?
Any important dates coming up? I always find timelines interesting - why did this crime HAVE to happen on that day and time? Was it random or connected?