My ex sister-in-law has been unable to let go and move on following her divorce 20 years ago. She has focused her attention on various members of the family during that time and sent them numerous long rambling letters and emails accusing her ex-husand of all sorts of things. She has sent packages of 'evidence' to back up her theories including her ex's credit card statements which she admitted obtaining without his agreement. Her letters and emails to myself and my husband have become more abusive over time and she has in recent years started to target our daughter as well. Her most recent letter to us included abusive references to our son so I am worried that he may be her next victim. In addition to the letters she has left abusive messages on her ex-husband's company answerphone, and on his mobile phone. Her ex (my husand's brother) has been forced to with-hold his address from his own son and daughter to protect his new family from their mother's unwanted attentions. There have been other more serious incidents including her (and her daughter's) harassment of an elderly couple who she mistakenly believed to be her ex-husband and his wife even though she did not come face-to-face with them. The elderly couple were extremely traumatised by the experience and reported the matter to the police. This irrational behaviour can't be considered normal - is it a sign of a specific illness? How can we get her the help she clearly needs?