Do you know if her lungs sound congested or not?
I'm sorry, but what
your describing DOES
NOT sound like
CHF to me....I think you need a new Vet!!!
With CHF, the cough is usually after excitement, exercise, worse at night & early morning and pretty much consistant.....Since your dog has this off and on, This sounds more like Asthma/Bronchitis & the treatment is completely different.....Bronchial dialators, cough meds., Inhalers & limited Steroids are given during these attacks....