Excellent, thanks for the additional information. This is very helpful.
Trissa is showing all the clinical signs for Canine Infectious Tracheobronchitis. This is just a very fancy name for Kennel Cough in dogs. There are many causing agents. Most of the time it is just normal bacteria in the nasal cavity and throat that take advantage and begin infecting the throat.
I have placed a link here for additional information about this disease:
They do mention a lot of detail, perhaps way too much. You have caught this in time to be able to use home remedies. This disease causes inflammation of the throat and trachea. The inflammation in the trachea produces the reflex secretion of fluid to try help sooth the sore trachea. This is why Trissa is coughing up the white foamy stuff.
Because she is still active and eating okay you are more than welcome to use these tips to make the healing phase a bit faster. It does not sound like she is a diabetic. If she is just use the pain killer please. You can:
Offer her aspirin at 10mg/pound once every 12 hours for 2 days. you will need to weigh her to work out the exact dose. This must be given with a meal. This is the pain killer.
The other is dry toast, almost black toast. Spread a rather thick layer of honey (not syrup) on it and offer her one slice in the morning and one in the evening. Honey has amazing healing capabilities. It is an anti-inflammatory, anti-histamine (the histamine release in this disease causes the itchy, scratchy throat) and antibacterial properties. So this will work on everything that is causing the problem here.
She is still quite young so I do not expect any complications. If she goes off her food and becomes depressed than a vet visit is indicated. For now home treatment is the way to go. Sounds like you have caught it in time. This will hopefully speed up recovery. The usual length is 4 to 6 days. Difficult cases can take 24 days to recover!
If you have other dogs at home there is a chance that they begin this cough too. You can apply the same treatment for them if this happens.
I wish you and Trissa all the best and a speedy recovery.