It could be but its most likely something else. Even though lung Cancer is diagnosed in more than 225,000 or so Americans every year its still is a small number of people, even smokers who get LC. Smokers even heavy current smokers only get LC at a rate of 15-20%. Non smokers are anywhere from 20-30 %. The rest are former smokers of more than a decade.
What is now known is that if you have a family of cancer regardless of type you may are predisposed. Get he seen by a well know cancer facility as soon as possible and make sure she gets a low dose CT scan..if there is anything on it then she should have a life broncoscopy done.
I am posting another information source for you.