Alternatively, your fiancée can seek employment with a school in Shenzhen and live there -- there are direct coaches from HK airport to Shenzhen. It is best to have a government school (primary, secondary or post-secondary) as your primary employer. Salary should be CNY 5,000 to 6,000 per mo. + free flat, utilities, local calls & Internet link against a 16-hour weekly teaching load.
If she seeks in the private sector, she will be working evenings and weekends, and some private employers are of very moderate honesty whereas if a government school commits a breach of contract, she can appeal to the Foreign Experts' Bureau, who will come down hard on the school if she has a case and can document it.
Try
Dave's ESL Cafe for starters -- they're hiring now for September and October starts.