Negative sweat test but lots of mucus

Well our 7 year old daughter came back negative on sweat test. Which is a relief but leaves me puzzled. My neice is a carrier. We just found that out. My daughter has to "heeeave" throughout the day, every day, to work up the mucus and spit it out. It is just part of our daily life. I just don't know what else would be causing all this chest mucus? Any ideas? I hear it is very rare to get false negative on sweat test, even for an atypical cfer. Perhaps her original diagnosis of asthma is correct? I just don't know. We've watched videos of asthma and CF on YouTube together. The asthma videos she says "no I don't feel like that." but with CF videos and vlogs that describe the mucus and cough she says "yes! That's how it feels!" I know she doesn't have the traditional bad CF. But what else could mimic atypical/mild CF? Feeling lost at the moment. Going to dr again next week. Maybe this is just the way it is with my kiddo. Any ideas or input would be appreciated.
Source: Cystic Fibrosis Newly Diagnosed Forum - Category: Respiratory Medicine Authors: Tags: Newly Diagnosed Source Type: forums