From the Malifaux Tactica Wiki:
Mei Feng is a melee caster. She excels at fighting multiple opponents, being able to dart into combat using her own constructs as stepping stones, once engaged she can move from opponent to opponent laying down damage and burning tokens. Mei Feng can combo her spells and strikes together into chains, which though card intensive allow her to pull off some impressive feats.
When starting a Mei Feng crew, you will have to buy the Rail Crew box set (Mei is not available to purchase individually at present). This allows you to build a crew for either Arcanists, or 10 Thunders, which will affect which other models you may wish to purchase. The Rail Crew contains Mei Feng, Kang, the Emberling, and 3 Rail Workers. This is all that you need to play either an Arcanist crew, or 10 thunders crew at the 25 soulstone level.
Mei can hire fire gamin, metal gamin, Willie the demolitionist, and a Rail Golem regardless of which faction she is used with. She may never use any models which have the frozen heart ability.