Oh Cherry I'm so sorry for you and DD . This was the hardest thing for me in the early days after DD1 was diagnosed. I used to give her pre-school a box of biscuits for her to have at snack-time and if there was going to be any baking/cooking going on, they would warn me and I would take in gluten-free substitutes so she wasn't left out. In the end, they just used to use gluten-free flour for everything, so that all the children had the same and DD1 wasn't excluded at all. Her teachers often bought gluten-free treats for her as well, which was lovely of them.
It is horrid - I tell DD1 that being coeliac and having to have gluten-free food makes her special. For birthday parties, I always make her up her own little picnic, but I try to find out before-hand the type of thing they are going to have so that hers is as similar as possible. And I make sure I have one of her cakes so that if they do eat birthday cake at the party, she isn't left out. Often the mums will ask me what she can and can't have so that they can prepare her a special party bag.
One thing to bear in mind - do they have play-dough at your DD's school? If so, they probably make it themselves and you should ask them to start making gluten-free play-dough. Not that your DD at 4 y.o. is likely to eat it, but the contamination of it on her hands could cause a reaction. Here's the recipe:
8oz rice flour
8oz corn flour
8oz salt
4 tsps cream of tartar
16 floz water
2 tbsps vegetable oil
food colouring
Cook all the ingredients over a low heat for 5 minutes (you need to keep stirring as it comes together quite suddenly). Then knead it on a board to remove the lumps.
I'm so pleased for you that her health has started to improve. She will get used to it and also will learn what she can and can't have. Perhaps you could ask her teachers to keep you informed of any cooking etc, so you can supply gluten-free alternatives for them to use.