I have taught writing/composition to a varied age of students over the years, and I must agree, to a certain extent, with some of the detractors as to the veracity of a 12 year old Taiwanese to be able to express her self so creatively and eloquently on such short notice.
Having said that, I will certainly give the OP the benefit of the doubt (obviously there are none on his part) as to the ability of this student.
What I would suggest, as would others, a controlled situation to double check this child’s writing skills.
What with palm pilots and wireless whizbangs abounding today, there are certainly many open possibilities to deception on the student’s part.
However, what must reign supreme is the teacher’s confidence in this particular student’s performance. If her parents are paying good money for her English education and would fit her with some sort of electronic cheating apparatus they would certainly be shooting themselves in the foot.
My suggestion to you is to do what I have done in the past just to break up the routine in my composition classes: Write out a different assignment (obviously with no prompting) for each student and then closely observe the student in question as you roam around the room.
I don’t know what your setup is, but any composition class worth its salt is divided into prompting, explanation of particular grammar skills that will be looked for, and the style that is demanded of the topic presented.
My classes are usually 90 minutes with the first forty minutes given to the above requirements and after a 10 minute break (which few take) followed by 40 minutes of writing.
During this time of 40 minutes of writing, I am (between sips of coffee and walking in and out of the room) very aware of what is going on in the room. The students know it, and they know better than to betray my trust lest I put out a cigarrette in some student’s eye or navel.
Didn’t mean to preach to the choir, but if you have a student as versant as this girl, you have come upon a jewel indeed. I’ve had two or three over the years, but none as creative and fluent as the one you have. I’m sure you realize the gravity of your responsibility to her future in English.
Who said composition can’t be fun!