Yes it was shown in the documentary 'A Royal Family' by Marcus Mandal & Anna Lerche about Christian IX and Louise's descentants. Ingeborg's grandaughter the late Grand Duchess Josephine Charlotte of Luxembourg nee Princess of Belgium told about it. I'm not completely sure, but I think the story was something like the following. Just before her mother Astrid died in the horrible car crash, Josephine saw that her mother had a grew lock of hair and she told her mother she would die soon (not knowing it would come true). Astrid wrought about this in her last letter towards her mother Ingeborg and she was offcourse already in shock after receiving the horrible news about the death of her beloved daughter and even more after reading the letter.