Annie had to have all of her teeth extracted at 5 yrs old. She was a breeder in a puppy mill before I got her and they did nothing to keep her teeth healthy. She was 5lbs and did just fine. If you have a good vet and trust him, just take a deep breath and do what you know needs to be done. Think how happy she will be to not have that broken tooth to deal with any more.
Good luck, let us know when it gets scheduled so we can say a little pray for you both on that day.