
Hi and welcome to the forum :)
Re the tests, if a comprehensive range of bloods were taken and found to be clear of anything suspect then I'd await results from a faecal sample before going too far down the test route (TBH, I'd have expected this to be done if not before then at least along with bloods).
Your little one could have a minor ailment which may well be cleared up addressing diet alone after ruling out or treating medically for something like SIBO (small intestinal bacterial overgrowth) or giardia (a parasite treated with wormers other than routine).
If food sensitivity is decided by your vet to be the most likely cause, it's not particularly easy to recommend specific foods with the absence of knowledge on what ingredient(s) is/are causing flares to her digestive system. There are several fish based diets available in complete foods both moist and dry versions but it could be that the bulking agents (such as rice, potato or numerous cereals) prove to be problematic for this little dog or even certain types of fish - i.e. OK with say white fish but not oily fish like salmon or vice versa.
As to the appearance of her stools, (the 'sausage like' analogy) - don't worry, dog folks have no qualms about explicit poo descriptions :-D If by sausage like you mean they appear to be covered in a skin - basically a mucous - then this is often a sign of an irritated gut and when the ideal diet in the ideal quantities is fed this will reduce however does require the GI system to be given time to heal. As to them being 'green' as she's still grazing this is most likely to be down to the grass :)
I personally rest upset systems in adults by 24 hour fast since last episode of a problem then giving small quantities of a food known to be suited to the individual. In the case of your dog of course your vet still needs to establish which ingredients (if any) need to be avoided.
When resuming or changing onto a food, adding a natural product such as Slippery Elm (or Dorwest Treebark Powder) to it can help naturally heal and soothe the gut although your vet may prescribe pro-kolin or similar to start her off at best advantage.
There is a lot of very good advice to be had on forum and when you have more info from your vet as to the cause there will be no shortage of suggestions I'm sure on what foods are available that don't require to be on prescription :)
I hope this info helps a little meantime - it is intended merely to avoid you being unnecessarily alarmed or disheartened at this little darling's problems - many of us have had similar issues at some point or another or know someone else who has!
very best wishes meantime,
Teri