You are the only one who knows what you child can process some kids are ready some are not . Sounds as if she is a very ready girl, I think the truth about the girls desease and the loss of socal freinds should also be explained so she can be ready, to so to speak, defend her freind. In a way you have time to prepare her for it all. My daughters freind (one of my best freinds son) died of an pool accident . It was only a couple hours from playing with him to a call that he was gone . He was 6 and my daughter was 5 . That was hard to explain but I must have done it right cus after seeing this thread she told me how she apprechated how I handled it. (who would think at 22 she would still remeber it) . Just keep the talk going between your selves let her know if she has questions you and she can try to find the answers together. It could be a way to strenghten your bond as well.
Kids can get asome really weird messages as information ,it can really upset them so keeping communacation open you can make sure she has the right info.
Prayers from Montana are going out to your family and the little girl.