why did Hanneli appear in anne frank's dream???

Hanneli was Anne's best friend. Anne had to go into hiding without warning. She had to go into hiding without saying goodbye to Anne. Hanneli was told the family fled to Switzerland. She was devastated. Anne felt guilty. Anne writes of a haunting dream in which Hanneli is dying and asks for Anne's help. In her diary, Anne questions why she lives while Hanneli does not.