If it takes a while for peoples teeth to grow in it's because they have strong teeth, i got told that when I went to the orthadauntists, tell her to be pathient and relax. =)
I can't remember when you start losing teeth. It is at about 6 or so? But I have news for you. They can keep coming in until up to about age 21! The very back molars are the last to come in.
The teeth that are growing in the back of her mouth are third molars aka wisdom teeth. There are 32 teeth in your mouth for some and some have these third molars pulled because of the lack of room in your mouth for them. You have two sets of teeth baby teeth which fall out and are replaced by your adult teeth.