How long does it take for my fiance to get a fiance visa for uk?

Waiting time depends on location you are in, your Embassy work load, etc. Depending on the case, application data and provided details, visa application could take from several days to several month to be reviewed by Consular.

I can take also 3 months. Best way to shorten waiting time is to use a courier (it can be 24-48 hours in some cases). Courier services can cost between $100-150 it worth it if you don’t want to wait for weeks or months.

Some couriers services:
http://www.allstarpassports.com/
http://www.globalvipservices.com/
http://internationalpassportandvisa.com/

Very important aspect is data provided in your applications. Fill your fiancée visa application very carefully! If you are not sure than hire fiancée visa attorney or consultant with good testimonials. It could save your time and improve your chances to receive positive decision from the Consular.

Important and useful information is also published at UK Border Agency website.