172 Skyhawk.
The O-360 is currently in use (since 1996) on the Skyhawk, but I was actually thinking of the O-320. Cerebral flatulence.
Pretty much any piston aircraft engine will idle at 600-800 rpm. And pretty much every running engine will be idling when people are walking around.
IMO, the only reason the young lady wasn’t fully Cuisinarted was that she just barely brushed the prop arc. Had her path taken her more fully into the prop plane, there’d be nothing left but a set of lower legs plus a bunch of goo. As it was the prop tip brushed her head & shoulder & got whichever hand was swinging in front of her as she walked into it.
Marshallers 
The people with the wands who direct airplanes in to park & who supposedlly are watching the whole airplane & parking area to avoid collisions or other hazards.
(Note that with helicopters, the “props” are call rotors.)
How did that happen? The main rotor moves air downward, so - provided you are below and not above it - it shouldn’t be capable of “sucking” a hat off your head.
A stiff wind + the helicopter coming up from behind me, all sneaky-like?
Okay - that works.
(One of those stealth helicopters, no doubt.)
A little more on this incident: Lauren Scruggs, Model Hit By Propeller, Was Warned By Pilot | HuffPost Life
Here’s a picture of what appears to be the passenger entrance. It actually looks kinda dangerous to me, possibly difficult to clamber or or out of. Perhaps more of the fuselage opens downward, but the bottom lip of the entrance as shown is pretty damn high. It also looks conceivable that a passenger could misplace a foot on the landing strut or wheel, and stumble a foot or two forward right into the prop.
I dunno, is here something I’m missing here?