True. Though one could argue that a lone attractive female would stand out in just about any city in the world.
I think standing out and being in danger are two separate things. I don't think just because a woman stands out in Istanbul (or any city) because she is attractive and she is alone automatically put her in dangerous.
What I had meant to say was that because lone women stand out more, it's more believable that a street vendor would have noticed and recognised Sierra.
Also, there are far fewer women alone here than in other cities. Not necessarily because of anything to do with danger, but just a culture where people prefer to do things in groups. Sometimes I go to a cafe on my own, and I will almost always be the only person alone. Not so in London or New York.