You are going to need to separate the dogs when feeding to be sure she is getting adequate nutrition and eating. You should also deworm her as internal parasites can definitely cause a dog discomfort. Common dewormers are Panacur, which is a prescription product so you need to obtain it from your Vet and it works on roundworms and whipworms. Wormers labeled as Pyrantel Pamoate are the best over the counter medication for roundworms. Drontal plus is also a prescription product and is used for the treatment of Tapeworms, though dewormers with praziquantel work well against tapeworms. Revolution and Interceptor as well as other heartworm medications.
Many different things can cause constant panting. Heavy panting can be caused by heart problems, lung problems, fever, or bronchitis. You can read about this here:
Dogs pant for various reasons. They pant to cool down, but they also pant when they are under stress, in pain, or afraid. There can also be medical causes such as neurological problems, respiratory disorders, and Heart problems such as heartworm, anemia, and fever.
It may be that she is coming into heat causing some hormonal changes putting her under stress and causing some panting. Keep an eye on her vulva for swelling and possible blood show to indicate her heat cycle has started. You will want to keep her away from other dogs as she is not mature enough to be carrying puppies herself yet.
I would have her seen to at least get her vaccinated. She may have survived Parvo, but she is still able to contract distemper and other diseases that the puppy vaccination will help prevent. Also, most states require that dogs be vaccinated for rabies at 16 weeks of age.
I hope this information is helpful to you.