Hi, I have no idea, our dog Rolly doesn't have this symptom. Is she on any medications? Walking her if she is up to it might be a good idea, you can always try it, however make sure she is warm enough and won't catch any viruses where you walk her, as their immune systems can get a little overwhelmed with lymphoma. I am not sure if a humidifier might help? Good luck and best wishes, hope she is feeling a bit better soon!