BlueDevil wrote:
If you marry outside the US, you must take the Direct Consular Filing (DCF) route. 
BD,
There are 2 options if you marry outside the US: K3 or CR-1/IR-1.  DCF is only available in a limited number of countries.  And it's basically doing the K3 or CR-1/IR-1, but directly with the US embassy in that country, instead of sending it out to Service Center in the US.  Much faster.
K3 gives the person a 2-yr spousal visa (multi-entry).  Before the 2 years are up, they must apply for a green card.  She can't work until gets the green card (or work authorization card), 3-6 months.  
CR-1/IR-1 gives you permanent residency (green card) upon arrival to the US.  She can work right away.
Like BD said, 
K1 is a one-time entry visa good for 90 days.  After the 90 days are up, she either has to be married to the US citizen who petitioned her or go back.