c dif questions

My sister in law just died of C DIF, why?  She was sick for a month. First the doctor said it was food poisoning and sent her home. She got sicker, went back, and asked for blood work, etc. He finally diagnosed her with C dif, and put her on anti biotics. She was so sick she had to take a taxi home and crawl down the stairs. She had diarrea, she couldn’t eat or hold anything down. She called my mother in law the day before she died and said "I am so sick, so so so sick.". Her roommate found her the next day in a coma, her blood sugar was so low she had passed out. She had several siezures, her liver shut down, and the bacteria spread to her lungs. She died two weeks ago, never coming out of the coma. She was admitted into the hospital the day she was found in a coma, and died two days later. If she had lived she would have had severe brain damage. We don’t know what happened, we know so little about C dif. Should her doctor have admitted her into the hospital if she was this sick? Was there something we could have done had we known sooner? Can c dif spread to your lungs or could it have been something else?
Can anyone shed light on this for us? My mother in law ineeds closure. Sharon was 33 years old.