[Nyororin]

I say to go with something simple. In Japan, teachers are generally not allowed to accept gifts from students, so there isn`t really any specific "teacher gift".

But really, why go with something "Japanese"? She isn`t living in Japan, and may be happier with something non-Japanese.
I mean, think about it - if you were working abroad, would you be thrilled to get something normal and boring from your home country? I wouldn`t... Don`t worry about where she is from. Just get something nice and small, and give it while saying thank you.