She is expected to make a full recovery and was released midmorning Thursday, he added. It was not immediately clear if she would stay in the Alpine republic or return to Britain.
Mills, who uses a prosthetic leg, recently bought a house in southern Austria and is training there for the 2014 Paralympic Winter Games, local media reported.
Broadcaster ORF quoted Mills as saying that she crashed into a plastic pole that had turned as hard as steel due to the cold.
But she seemed to take it in stride.
"That's skiing, you know," ORF quoted her as saying.
Mills, a former model, married ex-Beatle McCartney in 2002. They divorced in 2008.