Upvote:2
The correct answer is: she has to apply for a Marriage Visitor Visa. Otherwise she may be accused of migration by deception and deported. An authoritative explanation can be found here: https://www.gov.uk/marriages-civil-partnerships/foreign-national
Additional documents will be required. You are advised to contact the local council at minimum 2 months ahead and ask for details! Rules
If your future wife is divorced in China you will have fun, lots of it. To the point that it is maybe advisable to marry in HK and register the marriage later in the UK.