But now the firegirl won't leave. I used moveobects cheat to move her outside closer to the firetruck, thinking maybe she was in shock and needed a hand to get outside, but she just stands there. I did think about just deleting her with moveobjects cheat but I can't touch the firetruck and I am afraid to delete the girl and leave the truck there.

What do you guys do in this situation?

And why did this happen? When the fire started I had EVERYONE call the fire department including the kids, I was a bit panicking and wanted to be sure that the fire department would come, could that be the reason?

You can try save and restart the game, firefighters should have left by then.

If you have testingcheatsenabled true, you can shift+click on them and do objects... delete to get rid of them.