Gingrich has spent a lot of time courting her. This endorsement (assuming accurate reports) says a lot more about him, than about her or Romney.
Haley has been no stranger to criticizing Gingrich in the past:
On May 17, 2011 (well before the Newt surge):
Gov. Nikki Haley hammers Gingrich over Medicare remarks
Dallas (CNN) - Former House Speaker Newt Gingrich might not want to count on a presidential endorsement from South Carolina Gov. Nikki Haley.
In an interview with CNN Tuesday, Haley sharply admonished Gingrich for his comments over the weekend disparaging the Medicare plan proposed by House Budget Chairman Paul Ryan as "radical change" and "right-wing social engineering."
The remarks opened a floodgate of conservative criticism, with elite opinion writers on down to Iowa voters accusing Gingrich of throwing his own party under the bus and making it easier for Democrats to attack the Ryan plan.
You’re not actually here to say that Romney is best for the nation, are you?
Saying no to Newt doesn’t give a free pass to endorse Romney, by people who call themselves conservatives.