Dead battery puzzler- help find my short,..

So my friend has this '92 pontiac grand prix with the 3.4 (3.1, 3.8?)

6 cylinder auto, power everything, in a lovely classic white that's given reasonably good service for ten years as these things go. The battery's 2 years old, she thinks, no date. She had a dead battery and the car sat for a week before I got over to jump it, by which time it was down to 5v. Obviously a continuous draw with the car switched off. So I disconnected the battery, charged it overnight and started the car. The alternator puts out 14.5vdc. I then notice the kick panel light is on. "Yeah, it's been on for 2 weeks,.. does that run the battery down? The dome light used to be on too all the time but it burned out,.." So I dismantle the dash board and remove the bulb, hand her a flashlight and zoom, off she goes. Two days later she calls, dead battery. I charge it up again and as soon as I hook up the battery I notice the voltage dives about 2 volts so I pull the fuse with the interior lights on it and there's no difference. I pull the no.2 fuse and the voltage goes back up to normal. I start the car but there's no alternator output. I put the fuse back in and the alternator puts out 14.5v. All the exterior lights and accessories work normally except the seat belts don't suck back into the door the way they should. I notice the "passive restraint" gizmo is on the no.2 fuse circuit, as well as the "light monitor module", whatever that is. Can anyone think of something to try? Thanks and happy motoring to you all. nh.