Well, it does make a bit more sense with respect to why she wrote it when you consider that a number of people in her life had died or committed suicide, and IIRC she had a baby who died as well. Combine that with talking to people about ghost stories and reading about emerging science at the time, she apparently had an image of a mad scientist feverishly at work and she thought it would be scary and fascinating to make the story about a scientist discovering the essence of life.