Will she eat dips? Dd will eat sour cream and chive dip. The M&S one is the highest fat / calorie content. Dd will eat this with Doritos or similar. There’s a garlic one with about the same content, perhaps others too.
Dodoni crisps are baked with cheese on. Or just crisps in general if your dd will eat them. I always went for the highest calorie content.
Chocolate spread (the Cadbury one is nut free) or Nutella on the toast.
Nuts. Some are more nutritious than others. Idk which as dd won’t eat these.
One thing I do / did with dd is to eat crackers with butter and marmite on top. After months of doing this, dd having eaten toast with ketchup for months suddenly picked up a knife snd ate some butter. So eating something you want her to have at mealtimes can work.
Carrot sticks or crackers and hummus. Moorish has the highest calorie content and is a source of protein. Available from Asda, Sainsbury’s and Ocado. Sainsbury’s only seems to have the smoked one, which dd didn’t like.
Fridge raiders for the protein. Pepperami do something which looks like nuggets now.
I know CAMHS wants your dd to gain weight. However, not losing weight is an achievement in itself. With my dd she gained a bit of weight then her weight stayed about the same for a few months before gaining a bit again. Recovery can take a long time and not everyone can go at a fast pace.
As for foods being repetitive, I get you want variety. My dd can’t eat variety. She eats the same things every day. But some of the things she eats are calorie dense. She takes a good quality vitamin tablet alongside.