Good, safe site for an elementary school child to find a pen pal in Taiwan or China (preferably Mandarin)?

Our daughter is in Second Grade in a partial-Mandarin Immersion program. Her math is taught in Mandarin, while her reading and writing are taught in English. She would like to find a pen pal overseas. Although her focus is places where people speak Mandarin, I’m sure she would be interested in a pen pal from somewhere else too.

Thanks for your ideas.