Yes. You can take your Helper to China but you cannot ask her to work and let her stay there for a long period of time. Helper should have a special visa entry from Immigration. The employer also needs to have a supporting letter from the Hong Kong immigration Department.
Please be reminded that working in China is illegal for Domestic Helper who is holder of HK Foreign Domestic Helper Visa. It can result in substantial penalties to both employer and helper. You may also contact the Immigration Department for further information.
Currently, only expats in Guangdong province including Hong Kong and Macau residents can apply for a work visa for their domestic helpers. Chinese nationals are not allowed to hire a helper to work in the country.