Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern about Wendy.
Unfortunately, dogs eat all sorts of things that they shouldn't but, fortunately, most of them will pass whatever they ate with no issues. When it comes to a hook, though, there's going to be the concern that it might become lodged in her intestines and might require surgery to retrieve it.
But, having said that, there's the equal possibility that it will pass on it's own....which sounds as if that might be the case since she's developed loose stool with blood. This is pretty much what I might expect since the hook is likely to cause some irritation to her intestines.
While the presence of a small amount of blood is often concerning, it doesn't have to be alarming unless there's a profuse amount of it.
So, what to do now? I'd feed a bland diet of boiled, skinless, boneless chicken breast and 20-minute, boiled white rice which may help to settle down her irritated intestines.
I'd start a canine-specific probiotic such as Forti Flora which may be available at local pet/grain stores or can be purchased online.
I'd continue to monitor her stools for evidence of the hook.
However, if she becomes lethargic, starts producing large quantities of blood, stops eating or appears to have abdominal pain , then a vet visit would be wise.
I hope this helps and that you see evidence of the hook soon. Deb