Ooft that’s quite the combination!
You need to look at what staples you can get in - rice/pasta/potatoes/noodles etc are all really easily made gluten free and vegan when you get the specialist options!
Is she there over Christmas? If so for her roast she can have potatoes cooked in olive/vegetable oil, roasted veg, maybe a nut roast? There’s a lovely walnut and cashew roast on vegan recipe club that is adaptable for gluten free if you use gluten free pastry! Just roll have a gluten free ready made pastry that I’m nearly positive is vegan. Lots of supermarkets have vegan alternatives that are gluten free - gravies, potatoes, puddings etc.
For normal teas it’s probably really easy to adapt what you’re having.
Sausage and mash with free from gravy granules and veg - I don’t know where you shop but lots of vegan sausages are gluten free, I know Linda McCartneys are!
Lasagne/Spag Bol would be easy too using gluten free pasta sheets, vegan mince and jarred sauces. Double check whether they contain garlic but a lot will be gluten free. If not a really simple gluten free roux is easy to make!
A few easier teas would be a jacket potato - beans and vegan cheese with vegan coleslaw and salad?
A nice five bean chilli? Heinz do one!
Leftover bolognese!
There is also vegan tuna which is a bit like marmite, you love or hate it! If she likes it you could make a tuna Mayo.
Another easy one may be a burger/hot dog. You can get gluten free rolls by promise and they’re really good.
If you’re looking for a more traditional winter selection there’s also the option of beef casserole/steak pie. You can get a dried meat replacer called TVP (textured vegetable protein) and you soak them in water to rehydrate them. You then add them to stock/gravy and they take on flavour and are really tasty you can get them in most supermarkets. My favourite is a fava bean one from Ocado but any would do - you could even use veggie mince! Fry off an onion, add vegan stock cubes - oxo do beef ones, I don’t know if they’re gluten free sorry! Fry the ‘meat’, if a stew add lots of veg and seasoning, wine and water and let it bubble you can thicken it with cornflour. If a pie top it with the pastry I mentioned before?
Easy aisle options are great nowadays - you can get gluten free pizza bases and lots of veggie toppings, even vegan pepperoni!
Old El Paso do a gluten free fajita kit that comes with wraps and seasoning you could add lots of veg or alternative chicken piece?
A nice mushroom risotto and salad would be lovely.
A proper vegan chilli with rice, cheese, salsa, guacamole etc. You could also do nachos with corn chips!