George - I am not Coeliac but have severe Non Coeliac Gluten Intolerance and only diagnosed late in adult life. The issue with food and social life is harder for an adult in some ways but children can adapt and it just becomes a part of life.
In fact, what I would advise is that you may as a family wish to consider going gluten free in all meals. It means more cooking from scratch and eating out involves some planning but many more places now cater for gluten free diets.
For example, today in my small provincial town I am going out for a pizza and a really nice gluten free pizza at that in a small family run restaurant that caters for gluten free diets alongside 'normal' people.
Don't forget, as a coeliac your DD will still be able to eat, meat, fish, eggs, vegetables, fruit like any normal person. Ready made sauces, stock cubes, breakfast cereals, biscuits, bread and surprisingly things like oven chips and the like are the only tricky bit as they contain both obvious and hidden gluten. You can readily by gluten free cereals now so she can eat pretty much with the rest of the family the rest of the time.
The only remaining thing I would add is many coeliacs are intolerant to lactose (i.e. milk sugar) and I drink lactofree milk which is readily available for supermarkets now and tastes just like normal milk. It is normal milk just with the lactose taken out with an enzyme.
Otherwise I agree with all the above comments about testing and so on.