Does she take heartworm prevention monthly?
Has she had any weight loss recently?
How is her activity level?
With her age and symptoms, it could be one of a few things. She is definitely going to need to see a vet for an exam and some tests.
If she has a fever, it may just be an infection causing the symptoms. It is possible that she has a respiratory tract infection since she has a cough, too. You can check her temperature at home by using a thermometer rectally, inserting it about one inch. Normal is 101.0 to 102.5. Anything over 103.0 is a fever. If this is the case, probably an antibiotic will clear up the problem.
However, a cough can also be a symptom of a heart problem. Your vet can tell alot by listening with a stethoscope. Probably they will be interested in doing some bloodwork and/or an xray of the chest. Weight loss and decreased energy are also symptoms of a heart problem.
Let me know if you have more questions about this.
Dr. Debbie
Veterinarian
Full time practicing companion and exotic animal veterinarian