The 2 possible things that came to my mind while reading this are;
1 - Like some people, maybe this dog is depressed and could benefit from meds. Does the dog "seem" depressed to you? The sulky teenager analogy, for me suggests depression versus rebellion. If so, maybe a vet checkup is in order. (hearing and vision check t the same time is a great idea for sure)
Like some people, is it possible she is developmentally disabled in some way? ( less 'sharp' than the other dogs)? Or Perhaps the dog is not confident which is why just speaking to her or approaching her freaks her out?
2 - This is a training issue and the dog needs to better see that you and your husband are in charge of everything. Food, play, toys, sleeping areas, who walks in first, eats first etc.
This sentence sticks out for me.
"She is sometimes very affectionate - first thing in the morning or when we come home, she is overjoyed to see us. "
Is anything special happening at that time besides seeing you? Extra toys, treats, pets - anything at all?
Sorry to ask more questions than provide answers, but maybe the answers to these questions might spark an idea.