Actress Heather Menzies-Urich, best known for portraying Louisa von Trapp in the 1965 film “The Sound of Music,” died Sunday night. She was 68. Menzies-Urich, the widow of actor Robert Urich, had been recently diagnosed with cancer, according to her son Ryan Urich. Urich said his mother died on Christmas Eve, surrounded by her children and family members.