Pyreneans are well known to go without food for days. Our Troy does the same sometimes.
I have found however that Troy generally does it when something bothers him and he is a bit stressed. This could be anything from not feeling well, to building works or road works next door etc.
We get worried when he doesn't eat at all for more than two days and take him to the vets.
We tried all sorts of foods for Troy as well when we first got him, even the dreaded Bakers. He ate each one for a couple of days and then turned his nose up again. We finally found
CSJ and he's been on this for three years and is doing fine. We have recently put him (along with our lurchers) on CSJ Command Performance 21 (which is salmon and rice) and he likes it and rarely leaves it now! The added benefit is that it contains glucosamine, chondroiting and MSM, all great for the joints.
I hope you can find a food she likes. Sometimes you have to be a bit tough as well. We take the food up after 10 minutes or so if he doesn't eat it.
We always add a little something, like a third of a pack of Nature Diet, or a bit of sunday dinner, tripe and chicken mince etc, but only small amounts as an appetiser.
Vera