"It looked like she was just stepping out," he said.
The family has been in touch with authorities in their efforts to find her. No one was available to comment after hours Sunday at Istanbul police headquarters. Crime in Turkey is generally low and Istanbul is a relatively safe city for travelers, though there are areas where women would be advised to avoid going alone at night. The Galata and the nearby Galata Bridge areas have been gentrified and are home to fish restaurants, cafes and boutiques.
Sierra's children, ages 11 and 9, do not know their mother is missing, her brother said. Betzaida Jimenez said the situation has "been a nightmare."
"I'm forcing myself to get up because I have to get up," she said.
But she said the tight-knit family was holding onto their faith.
"We're praying and trusting God that she's safe somewhere and we're going to find her," she said.
Associated Press writer Suzan Fraser in Ankara, Turkey, contributed to this report. Follow Deepti Hajela at www.twitter.com/dhajela