Visa for Vietnamese passport with New Zealand work visa

Hi,
My partner and I are planning on travelling to Shenzen (southern china area) for a wedding at the beggining of January, we will fly in to Hong Kong on the 4th January, and then out of Hong Kong on the 13th January. We do not plan on spending any time in Hong Kong, and will only go directly from Hong Kong Airport to Shenzen.

She has a Vietnamese passport, does she need a tourist visa? And can she get a multiple one, as we will have to pass through immigration from Hong Kong to China and then China to Hong Kong, or does she need seperate visas for each of these?