There really isn't enough information to say, but it the article makes it sound like she made a left turn without making sure there wasn't traffic coming up from behind her.

Left turns are dangerous for so many reasons, and we had this problem not too long ago on our shop ride when someone at the front started to move left in order to make a left turn at an intersection. He said, "clear back" and riders started to move left behind him, but the road was not clear, at least not for the whole group. Everyone was fine, as enough people didn't blindly follow him, but that, and this article, should serve as a reminder to check and double check for traffic before moving into a lane.