(well, she is actually playing at the broad end, but I know what you mean)....

Playing near the end close to where the string passes over the metal base bridge produces a 'brighter' sound. Some might call it 'tinnier'. But this is how it was usually done on the lap, or on a table...and most early 'harps had more room at that end, because it was designed to be played flat.
   After Maybelle Carter & others needed to be able to move back & forth in front of single microphones and play it held up against the chest, makers moved the strings down toward the base, to leave more room for real 'picking' and to make the entire 'feel' of holding it more comfortable.

There are many variations to the sound, depending on where the strings are struck, but usually playing near the center gives the best balance.