Tamari is gluten free soy sauce.
Rice noodles are great.
GF bread is generally shit.
Always check oven chips - the fancier they appear, the more likely they are to contain wheat. Except McCains, which are completely out. But Aunt Bessie's are likely to be OK.
Co-op have lots of standard products with GF ingredients where other supermarkets don't - sausages, burgers, meatballs.
GF pasta is best when it has corn, rice and quinoa.
Buckwheat noodles are OK if you check they're 100% buckwheat - Clearspring do them. But always rinse them straight away or they stick together in a lump.
Heinz beans and sausages are GF and so are many of the cheapest hotdogs. If she likes mustard, she'll either need to mix colmans powder or buy French's, as most ready mix mustards contain wheat.
Watch out for barley, malt vinegar and she might also have issues with oats, even gluten free ones, as avenin proteins can be reacted to in the same way as gliadin. Lactose intolerance can also be common due to gut damage.
And she needs to lock her food up. Otherwise some other git will nick it and/or cross contaminate her stuff.
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It's become easier for DP to just eat GF as well, as that means there's no accidental cross contamination. We had his and hers slots in the toaster, separate butter and peanut butter, etc. but I definitely got caught a few times before he decided it was simpler that way.