Yes, she has dual citizenship. Let me explain....
Iran does not accept dual citizenship. If your father is Iranian and you are travelling in Iran using an Iranian passport (no matter what country you are currently living in or are also a citizen of), you are an Iranian citizen, and therefore you are subject to the whim of the regime.
I am not defending her actions. When this story first broke, I had a hard time feeling sorry for her, because I knew that having been born in the U.S., she had to apply for Iranian citizenship. I still think that she and her father were very foolish, but she wanted to live in Iran and go to school there, so this was her choice.
However, she is being accused of spying - which is ridiculous - and therefore her inprisonment is unjust.
Americans travelling on American passports have been pretty safe - a lot safer than travelling in Mexico outside the resort areas.
It’s the Americans who claim dual citizenship as Iranians who have been and are, at risk. And they know it- they just think that it’s not going to happen to them.
P.S. If Iran starts to feel really threatened - like by Israel - then American tourists w/U.S. passports and Europeans for that matter, will be at great risk for becoming hostages. This summer is NOT a good time for anyone who doesn’t live in Iran to be travelling there.