Usually if they have nasal symptoms, it is a respiratory virus such as a cold. If she does not have nasal symptoms, it could still be a respiratory virus causing a "chest cold." But then it could also be something more serious such as bronchitis, pneumonia, or congestive heart failure.
Lift her lip and check her gum color. Her gums should be a healthy pink. If they look pale, white, or purple, she needs to go to the emergency vet right away as she is not able to circulate oxygen as she should.
If she seems to have difficulty breathing, or gets out of breath easily, then she should see a vet right away as well. She could have fluid in her lungs from pneumonia or heart disease.
But hopefully she just has a cold. You can try giving her plain robitussin cough syrup, every 6 hours, as needed.
When someone takes a shower, take her into the bathroom and steam out her respiratory tract.
Offer her extra fluids such as warmed low sodium chicken broth. Add water to her dog food.
If it is just a chest cold, she should be improving in a few days.
I hope this helps.