Is dancing dangerous for those over eighty?

My ex MIL, very healthy, remarried in her eighties a man nine years younger . They met at a Senior Citizens’ Dance Center. One night they were dancing and she had a stroke and fell to the floor. She broke her leg , they put a long rod in it and she never danced again. She never walked unaided again either.
Was it foolish for her to have gone dancing once a week? She died at ninety six.