Tunis is a great place to be I think as a teenager. They have IB schooling and she will be exposed to so many different languages. I think she will find herself quite popular being from America. I hope she is having fun making friends and eating great food. I don't know if she is into sports, but tunisians are big on soccer and handball. And she will be so lucky when school gets out. She will be able to head to the beach with her friends and enjoy the warm weather.
I am sure things are a little different for girls than for boys (less freedom, more time at home). As I am basing this of the experiences my dh has shared growing up in tunis.
That being said, there are many wonderful people in Tunisia and she will be better off having stayed there for an extended period of time.
My son went to Tunis when he was a toddler with my dh. So I know what you mean to miss them terribly. Luckily there will be kids eager to learn english, so she should have lots of laughs at their attempts.