Normal tooth decay doesn't hurt at first. If her teeth hurt, there is more than likely a serious problem going on, especially if this is soemthing keeping her up at night.
I have many, many fillings in my mouth. This is not something I'm proud of, but it's true. I also have several crowns/caps (is there a difference?) because I have gotten to the point on several teeth where there was more filling left than tooth.
The only two times in my life (I'm 41) I've ever had a tooth ache were when it was actually an abscess.
I've lost fillings before and had to wait a week or more before getting them replaced. Still, I've never had a toothache other than the two abscesses.
I think you need to get her in soon.