I have DC with allergies, but not to nuts. Their school has a "no nuts" policy which is flouted daily by many kids - it annoys me partially because we always are scrupulous about abiding by the policy, meaning my kids have even less range in their already reduced options for packed lunch, and also because parents of kids with nut allergies will be assuming it's a safe zone when it's really not.
As PPs have said, there's a growing school of thought that making schools nominally "nut free" is a rubbish idea, because there's no way the school can police it thoroughly enough, but also means they won't have safety measures in place for the child because there are supposedly no nuts around.
I'd have a big chat with the head about whether, if they're not able to police snacks and lunch boxes effectively, they're actually fulfilling their duty of care. The school might be better moving to a system of risk assessment and management.
For eg, fruit only for snack times, and then seating at lunchtime in a way that creates a bit of a cordon sanitaire for your DD (mine both had a space either side of them but a friend opposite, and a dedicated tray for their lunchbox so that they were not risking hands on table where there were food residues, etc. When they were little, they also had a dedicated TA either seated with them or hovering nearby. And then the school could enforce monitored handwashing by everyone before going out to play. They may also need to look at how furniture is wiped down.
I know it's horrible to lose your safe space for her - I can really understand that - but actually I think it's more dangerous for.her this.way than with school, you and her managing it as a team. My youngest is also 8, and is able to manage his exposure risks pretty effectively by himself - and he has five different allergies.
Parents who ignore the no nuts rules make my blood boil, but your next step is to ask the school to be proactive in working out how to meet their duty of care to keep her safe, rather than just saying "no nuts but oh we can't police it".
Big hug - not easy helping them navigate the world and keeping them safe x