How about being proud of your daughter for taking on the challenge of firefighting and wanting to do something that has been a part of your life for so many years? How about being impressed that she feels strong enough to jump into an obviously male-dominated environment? You of all people should realize that fighting fire has the potential to be much more exciting than waiting tables at the local coffee shop.
Chances are excellent that you have no need to worry about her safety. Try to remember how thrilling the prospects seemed to you so many years ago!