When it comes to people misstating what happened to them a decade before, sometimes we are too hard on them. It's a proven fact that our brains don't remember things perfectly. They just sort of capture the broad strokes, and then rebuild the details when we recall those memories. So a lot of times, we get things wrong and honestly don't realize it.
Of course, I'm not sure that's what happened to HRC. I wouldn't imagine sniper fire to be the kind of random detail your brain would use as filler, so the whole thing smells fishy from the start. But it's one possibility, however remote. Plus, if she knowingly lied about that particular detail, it's a really strange lie to tell, and a dumb one, because she should have assumed (or even remembered!) that there were plenty of witnesses to the event, including members of the media. So even if you are inclined to give her the benefit of the doubt, there's still plenty of room for both skepticism and bemusement.
And, of course, this whole River of Blood thing is entirely different. Trump isn't misremembering something that happened to him, or even embellishing his own personal history. He's just flat out making stuff up, because it looks good on a plaque on his property.