Very unlikely that she is still alive, given her age, poor health and the fact she hasn’t got her medication.
I think the most plausible explanation is indeed a kidnapping for ransom by someone perhaps connected to, for example, a gardener, pool cleaner, postman, window cleaner, etc, who will have mentioned who she is and that she lives alone, etc. Ransom plan obviously went tits-up and now the culprit may have a dead body to dispose of, which is a whole different scenario.
The stuff about unknown DNA is not helpful. EVERY house will have unknown DNA in it. Think about all the previous people who may have lived in or visited a house, plus every plumber, electrician, cleaner, grocery delivery person carrying groceries into your kitchen, etc over the years. Unknown DNA all over the place.
The theories about Trump/Epstein are just too wild IMO. There are much easier ways to get at someone without drawing so much attention. Think it’s also dreadful to point the finger at family members with no evidence - surely we can assume that the police have scrutinised the family and their alibis for the night in question.