hmm, sounds like the shift lock is malfunctioning. im not to familiar with S14 automatics but i know other older automatic imports share this same problem. (accords, camerys, etc)
to fix you can:
1) have the shifter replaced
or
2) i believe there is a shift lock override button somewhere on the shifter column. i know honda and toyota automatics have them, try checking your gf's S14, its worth a shot
they must be depressed to override the locking system in your shifter, good luck