Dear Tokarra9696,
I'm so sorry to hear about the medical issues your niece is suffering from. I am sure it is a very difficult time for you now since she is comatose and in the hospital.
Not knowing the full details of this case, I would say that it is possible that during the first admission to the hospital, she had not yet developed the symptoms of the pneumonia fully. The physicians may have felt that it was asthma at the time, perhaps based on her history, a physical exam, and her symptoms (if she was improved). It is also possible that she developed the symptoms in the few days she was home. Only her doctors can really answer this question in retrospect if they were the ones examining her.
Seizure disorders are also very tough on the body. When someone is seizing, if they have aspiration (breathing in) of something in the mouth into the lungs, this could lead to an aspiration pneumonia. The mucus on her face could have been related to the seizure--since patients who are actively seizing can lose control of their actions (and potentially body secretions).
If she is currently on a breathing machine (due to continuous seizures), this could increase the risk for a ventilator related pneumonia. There are many risk factors for pneumonia in her case. The organism and type of pneumonia also are important factors in determining the severity of her case.
Unfortunately, It is impossible to predict her prognosis or know how permanent or temporary this is. The best people who can give you this information are her actual physicians, since they are the ones who know her intimate medical problems, severity of illness, and extent of disease (like how bad the pneumonia is), so I'm sorry I cannot comment on this.
I would encourage you to have a dialogue with your family and doctors to address the concerns you have. I hope your niece has a quick and full recovery.
Best Regards.