Fox News ran this story too, not just CNN. And many other news outlets did, including many local outlets.
Am I missing something, but how do we know she was a "staffer?" Had she been a volunteer in some office somewhere, it wouldn't mean anything. The issue is whether she knew Clinton before this.
That image on the bottom, I can't read anything said in those Facebook posts to the right of it. Someone said the image was "old," but it clearly isn't. Clinton looks every bit as old as she does now, and has exactly the same hairstyle that she does now. It could have been taken after the hike rather than before. Or perhaps not. Perhaps this Clinton supporter wasn't telling the truth when she implied she had never met Clinton before, but there isn't enough information in this thread to draw a firm conclusion.
Finally, I would mention that this is nothing more than a puff piece about a candidate who lost an election and will almost certainly never run again. So I fail to see how a supposedly Clinton biased news source decides to run a fraudulent piece in order to prop up the image of someone who is politically dead. At most, CNN was misled here. And that's if the story is false.