An 85-year-old woman named Harriet, passes away. Her will, executed 1 year prior to her death, directs that her entire estate should pass to the home-health care worker who assisted her the last two years of her life. Harriet's two sons were very disappointed that they were excluded from the will. Is this a case of undue influence, such that the sons could successfully contest the will and receive the estate's assets? Please provide detained explain detailed explanation.