What do you think happened?

Ok so my sister ped away on march 19th 09. She just gave birth to a baby girl two months before and there was no known problems that she had. The night she died she got off the phone with my mom and only an hour or two later her husband who is a firefighter calls and says that she fell in the shower and hit her head. She had a huge walk in shower and there was nothing in there for her to hit her head on but the floor. So my parents load up in their vehicle and head two hours to her house. Not long after I find out she is in the hospital I get another call from my oldest sister telling me that she has died and my parents found out when they were on their way. When they got to the hospital she was supposingly gone for bout 2 hours but her hair was completly dry (she had very long thick hair) and there was no bruises anywhere on her body to indicate that she had fallen. Her husbands family was sittin in the waiting room laughin and crackin jokes not one tear in their eye. My other sisters husband heard his mother say how she went to her house and there was no blood anywhere in the shower. So we start wonderin how she had time within that two hours to go to her house. At the funeral they wouldnt let any of my sisters family see the baby. My nephew who is 15 overheard his mother talkin about how she went and cleaned her house that night. She has never cleaned her house for her. They didn't even cry at the funeral and her husband took her wedding rings off and kept them. To this day they won't let us see the baby and they have changed their numbers so we can't call. Even his brother who used to have the biggest crush on me wont talk to me anymore. The autopsy report says there is nothing there but they had to have something so they are saying it was her heart. Not to mention they were having prooblems in their marriage anyway and she wanted to leave him.