Hi Krissey,
My youngest daughter will be twelve in May. She has already had a palette expander and several top braces. She had a crossbite. She didn't lose her front top teeth until the second teeth had grown in behind them. My oldest was in braces at the time, and our orthodontist kept checking her. He began treatment when the top front teeth next to the two center ones were due to come in and he saw them on x-ray. She did very well throughout the treatment. She has not had anything on her teeth for at least a year or maybe longer, can't remember exactly. Since doing the treatment, all of her second teeth have come in perfectly, except for her 12-yr molars which are in not out where the pallette expander put the rest of her teeth. He said this can be fixed fairly easily. I was told before they began treatment that 80 percent of kids who have the expander will require braces. She was very late in losing her baby teeth probably because they were not being forced out by her second teeth. Once he corrected the bite, etc., all her teeth came in where they were supposed to.
I would suggest that you consult with an orthodontist. I think that having them decide when the best time to start treatment is important. As far as your daughter having a very small mouth, they may choose to pull some teeth to allow for room if they have to. We have not had to pull any teeth to date, but it is evidence that her wisdom teeth will have to be pulled when they come in as there is limited space.
I'm not sure why her second teeth on the bottom have not come in. Teeth fall out because the second teeth have broken down the roots of the baby teeth. Your dentist can answer that question, I'm sure.
Good luck.
R.