Hi Imaginaryfriend. You are getting some brilliant advice here. Just adding my bit, because my daughter is the same age as yours so probably has a similar social life! She is allergic to bee stings (which can also cause anaphylaxis). DH is severely allergic to nuts and we haven't risked giving her any yet.
Birthday parties are the hardest thing, I reckon. There are some mums who I trust to shop carefully for nut-free food, but there are others who can't really get their heads around it. I have a good chat with the mum when I accept the invitation and suss out whether I think she has grasped the need to read labels ultra-carefully. Also, whether they would cope with using the Epipens if they had to. If I'm not entirely confident, I stay at the party to keep an eye on things. DD1 is not always too impressed about this!
Even if I'm not staying, I ask the mum when I arrive whether I can have a quick look at the food and check ingredients if there are boxes around. I have been known to fish packets out of the bin to read the label. You learn to be quite assertive in these situations!
You also need to get your DD trained not to eat anything unless she has checked with you (or responsible adult) if it's OK. So if one of her little friends offers her a sweet at the school gate, you get a chance to check what it is. We also keep a stash of "safe" treats at home, so if I have to say no to something she is offered, she gets a treat in compensation later.
The other thing to think about is whether you have particular friends who babysit for you, or where your daughter likes to go and play without you. You probably don't feel like leaving her at all at the moment, but the time will come when you need to. You need to think about adults who you would trust to use the Epipen if they needed to, and take some time to talk them through what they have to do. I have also written out simple instructions for babysitters that are kept in the bag with DD1's Epipen, so they have something to refer to. In our case, it's more difficult, because she could get stung by a bee at any time - the risk is around even when they aren't feeding her .
Your school does sound clued up and I would agree that school dinners from an allergy-aware kitchen are better than packed lunches where there might be a culture of kids sharing food.
Sorry if I'm repeating what others have said - I tried to read them all properly, but I'm supposed to be working Try not to get overwhelmed. It is scary, but it is managable and the whole thing becomes second-nature after a while.