I'm so sorry for your loss and the terrible ordeal you and Rossi had to go through.
I know it's hard but try not to beat yourself up too much. It is easy to look back now and see all the signs and say you should have done something beforehand. I'm sure that if you thought for one second he would take it that far you would have done something immediately. When you remember her, try not to focus on her death but think of all your fond memories and the good times. It is clear she was greatly loved and had a wonderful life.