I don't know if they've ever given a real answer as to how she died in the video, but if you look at the video, when Axl is kneeling at her coffin, she has a black mask over the left side of her face. That's generally something that's used when someone dies in an auto accident or is disfigured in some way so they can still have an open casket at their funeral. So however she went, it wasn't pretty.