She doesn't look anorexic to me. The guys don't look that thin either. A bit rangy perhaps, but not emaciated. Also, how do you know they're tiny? There's really nothing in the picture to base them on. Have you seen any elsewhere?
I know that they have their tallest folk go to Panmujon, as does the ROK (5' 10" is the requirement I think) and even the U.S. (6'+ IIRC).
That said, in any conflict the ROK would wipe the floor with the NKs. Superior training, equipment, morale, logistical system, everything that matters.