Shortness Of Breath, High Blood Pressure, Diagnosed As Pneumonia. Had Wisdom Teeth Removed

Hi, my mother in law has been complaining of shortness of breath for over roughly 3 months now. She had her wisdom teeth removed last week in May. I was with her the June 20th-25th and she had shortness of breath, and in pain. She went to the doctor several times the last few months to find out what was wrong. Her blood work and everything came back okay. She would feel better one day, then bad the next. Last week she called an ambulance because she could not breath. She was in so much pain they put her on a ventilator and medically induced coma . Monday her heart rate was at 90, they did dyalsis Tuesday evening and she died Wednesday morning. They said she had some sort of pneumonia ... I do not understand? She was a very happy, outgoing, healthy lady. She had high blood pressure a long time ago... but lost weight and got it down right away. She had been to so many doctors the last 9 weeks... It is hard to believe she just had pneumonia... wouldn t they of found this doing basic test when a patient comes in complaining of Shortness of breath . Can someone help me get some answers? I feel terrible because how this turned out does not seem right.