Well, some of the possiblities could be that
A) her memory has better timings and therefore is faster than yours
B) since her comp is new she doesnt have any background progs sucking up memory while you may have alot.
C) she was visited by the magical computer fairy that overclocked it without her knowing
But seriously, people get so worked up over benchmarks. If you reformat and run pcmark again I bet you would probably get alot better scores.