Your girl friend should have to go around and let you out since only the passenger door had a lock. Even better have an extra key made so both of you can step out and lock the door. We put driver side door locks in some of the AD's we do but it is time consuming and a bit pricey. I'm in my 80's so I remember why the lock was on the right (or passenger) side only. Many small town streets were not paved so you slid across the seat to get out on the sidewalk rather than getting out on the left side and slogging through the mud to get on the sidewalk.

http://s32.photobucket.com/user/coilover/media/doorlock010.jpg.html

Evan