The easiest thing would be to take it to Honda.

I reread your post and now I'll try to explain what happened after I explain the how the automatic shift works on an Accord. On an automatic Honda Accord, you can shift freely between certain gears, (meaning you dont have to push down on the shifter button) N, D4, and D3. When in 1 or 2, you can simply push the shifter foward and it will move into the next gear, however when you try to go down a gear, you have to press the shift button. Thats all nice and dandy, but how the Honda automatic shifter works is a spring, and lever. If you disassemble the shifter, there is a long white stick that goes down the shaft and rests on a semi-cross-shaped metal object. The top part of the white stick connects to the metal object, and on the bottom it rests on a spring. When you press the button on the shifter, it pushes the rod down which moves the metal object, which then pushes down the spring in a way to allow you to shift gears. If the metal object become dislodged, the spring will be dislodged, and then it messes the car up and the electrical signals become messed up. Thats the reason you cant take your key out. The way to fix this yourself is to take apart your shift console, push the spring down, place the metal object in correctly, and then put the white rod in correctly, and reassemble the shifter. The hardest part will be keeping the spring down. Im sure that if you took it to Honda they'd just replace the whole thing instead of fixing it, and I have no idea how much it would cost.

When you had your gear set in 2, the spring would be depressed and the white rod resting. When you girlfriend moved it to D3, the spring would have popped up and the white rod would have shot up the pipe and at that moment is probably when the metal object was dislodged.

I dont know how to explain this any other way. I know its confusing, but I hope it'll make more sense when you take it apart and look at it. Lesson to be learned... dont buy an automatic.