Sierra was in regular contact with friends and relatives during her vacation and had told them on Jan. 21 — the day she was due to board her plane back home — that she would visit Galata Bridge, which spans Istanbul's Golden Horn waterway, to take photos. She never checked into her flight.
Sierra's mother, Betsy Jimenez, said her two grandsons did not know what had happened to their mother.
"Their father is going to talk to them when he comes back and we'll all be there to support him," she told NBC's Today show on Monday
Jimenez said it was Sierra's first overseas visit.
"She wanted to go take pictures of the history of the place... and she was interested in taking pictures of the bridges. She was fascinated with the bridges," Jimenez said.