My 7 week old daughter has a cough and she's congested. What can I do?

Cough in 7 weeker. Cough and congestion in a 7 weeker may be a viral infection or environmental etiology like house dust, allergens, etc. If she is not running fever you can use nasal saline drops and suction gently. Fi she has a bad cough you should see her pediatrician soon.
Nasal wash. At 7 weeks the primary cause of congestion is the environment. House dust, fragrance, perfumes, detergent or cleaning products all leave scents that may not bother you but irritate a babies nose. A good nasal clean out with saline can remove much of this irritant load, but removing the offending irritants from babies life helps more in the long run.Air particle filters can also help.
Coughing. Consult your doctor for cough medicine prescription & evaluate causes.