It's not teething. Teething will give them a runny nose, but it won't make them congested. Only an illness like a cold or something similar can make the congested. For now, just alternate tylenol and motrin (ibuprofen) if she has a temp (and remember to take her to the doctor for any temp over 100.4) and set up a humidifier in her room to keep everything moist and moving. You can also use a saline mist with a bulb syringe to try to irrigate and evacuate her sinuses. You can also fill the bathroom with warm steam from the shower and sit in there with her. This will help loosen up the mucous.
If she gets REALLY stuffy, meaning that it's interfering with her sleeping/eating/breathing, then ask you doctor if it's okay to use Neo-synephrine which is a decongestant that is administered as a nasal drop so no internal medicine used. It works GREAT. I was given some by the people in the ER for my son when he was 4mo. He caught a nasty out-of- state bug from my step-son that none of us had any immunity to. He needed breathing treatments and they gave me the Neo-synephrine to administer at home. You can only use it for three days though until you need to take a break because if you go for longer it can cause rebound stuffiness. It can be purchased over the counter at most pharmacies. Some pharmacists keep it behind the counter and some don't; you'll have to ask.
Do check into allergies too. Don't forget that. It could be anything from your detergent to the dog. If this doesn't resolve itself in the next week or so, definitely talk to your doc about some allergy tests.