Her family last heard from her by letter in August and she was found in December, so not that long of a PMI assuming she passed shortly after the letter. The family last saw her in person in April, at her father's funeral.
Sad that they couldn't figure out a COD. But with her having just lost her father, and the way she seems to have just sat down and died, I wonder if she may have taken her own life. Perhaps by overdose/poison. In which case she may have disposed of her handbag to get rid of anything identifying, though that doesn't explain the lack of shoes unless she took them off and they were taken by animals or stolen.