
How about sardines in sunflower oil, or pilchards. I don't feed raw myself as I don't have enough confidence to do it, or how about a little bit of grated cheese mixed in with the kibble, cottage cheese, natural yoghurt, cooked liver, cooked minced chicken or lamb. I haven't tried it with my dogs, but a colleague at work used to buy frozen rabbit from Iceland for her dog and he loved it. It comes in chunks I believe.
I feed my three dogs Arden Grange, but I always add some extras in rotation with their meal.
The Natures Menu tins are good too. They smell and look appetising. I sometimes share a can of this mixed in with the AG and it's always wolfed down.
The only thing I would worry about giving tuna every other day for a long period if it's tinned, is the salt content.
My female used to be a bit fussy, however she is 3yrs old now and she will eat anything put in front of her including kibble with no extras . Sometimes if dogs are having more food than they need, this can cause a bit of fussiness.
Anyway, hope this helps some. Good luck with your girl. Let us know how you get on. x