How old is she?
What are you feeding her for food and treats?
Has she had anything to eat besides dog food?
Do the whites of her eyes or gums look an abnormal color compared to your other dog?
I would start with having a fecal sample checked for giardia and whip worms.
Sometimes bright yellow stool can indicate a problem with the liver (inflammation and jaundice), the pancreas (lack of pancreatic enzymes), or the gall bladder (gall stones and bile). The way to determine if there is a problem with one of these internal organs is to have a blood chemisty run on her. Since she is still eating and not vomiting I do not think it is too severe at this point.
If you are feeding her anything that is light colored that can make her feces yellow as well.
Yes giardia and whip worms are curable.
If she has a problem with her internal organs it can be treated. It might be curable if it is caused by a bacteria. Then it could be treated with antibiotics. If she had hepatitis or pancreatitis or an intestinal infection those could be cured with antibiotics.
You are a great adoptive parent!