So he thought he could protect her in Syria?

"Mueller said she wanted to come, too. Alkhani resisted, saying Syria was too dangerous for an American. But he eventually agreed to Mueller’s request, because he feared she would find some way into Syria without him, and that he wouldn’t be able to protect her ...Mueller was shaking with fear, he said, but he assured her that they would be safe, and that the men would let them go once they realized the pair had come to Syria on a humanitarian mission." (thanks Laure)