I have opted back in into your question since no one had picked up your question and you had not received your answer.
Now that you have rephrased your question, I can understand the context of your question. Initially it seemed to be four very open ended questions which would be difficult to answer.
I am sorry for your loss. Although I can understand that the events must be turning over and over in your mind and you are trying to make sense of it, I am afraid that her condition was a very serious condition with a very high mortality rate. It was just unfortunate that she happened to have this rare complication, but once the complication developed there was little chance of survival.
Cardiac arrest in PE is a rare complication. Mortality is very high because it is difficult to diagnose and the effects are very rapid. Although you must have been thinking about the sequence of events and whether she received adequate treatment, I hope it gives you closure to understand that it was not the fault of her medical treatment, the complication itself is such that death is all too often the result. The exact details of what went on of course cannot be established now, but no matter how the treatment progressed, chances of death were always very high and based on this, it is safe to say that the treatment was not at fault, it was the tragic combination of her initial condition and its complication.
Hope this helps you in attaining some closure on this tragic circumstance at least as to whether her treatment was adequate or not.
Look up this study which deals with this complication:http://www.ncbi.nlm.nih.gov/pubmed/10826469