Does it happen any other time? Does she may any other noises or actions?
Generally it is a sign of discomfort and pain. Since your vet used a steoid and it stopped, it would make me wonder about pain. The problem is identifiingy it's source. Neck and back pain are not uncommon nor are problems in the chest. She's a bit young for any age changes, but the neck could be a source. Pinched nerves can cause changes in the way they carry their head. You may watch to see if there are any movements she is unwilling to do in the the movement of head and neck. If all her GI activities are normal, then the eating the food isn't an issue, and it would point to the movement, which primarily is in the neck.
The coughing issue could indicate a tracheal collapse, also common in her breed. That can be diagnosed by several radiographs of her chest. That could be another avenue to pursue and he could look at her neck in the same session.
I hope this is helpful. Please push ACCEPT and thanks!