I just read the Elizabeth Southwell writing. It is funny that the writing is called "A True Relation of What Succeeded at the Sickness and Death of Queen Elizabeth". This is funny because the whole thing is based on superstition.
According to Southwell's writing, Elizabeth died of one of two reasons. Elizabeth was completely healthy until she received the necklace that was said to kept another woman alive for 120 years. I am pretty doubtful that a woman in the early 1600's lived to 120 years, but I guess they believed it. So this health charm, made Elizabeth sick, according to this essay.
This essay also mentions a voodoo doll type item. Elizabeth's ladies found a queen of hearts card under Elizabeth's chair with a nail going through the forehead of it. Southwell probably believed that this was a cause of Elizabeth's illness, as well as I am sure a lot of other people did too at the time.
I looked briefly online at the sources of her death, and I guess we do not really know exactly. It was probably just simply old age, since she was 70 years old. But people will believe what they want to believe, as well as what others believe in their time. And since I cannot prove otherwise, I guess I should not rule these theories out.
This will stand in time as possible reasons: unlucky charm necklaces and voodoo dolls.
