Lisa,
I'm so very sorry that you are dealing with this right now. To me, it just seems like it is really unnecessary to talk about statistics with young children. And yes, they should be careful about what they say to them regarding this. Don't they realize how that could affect a child who has a loved one dealing with this disease? I have no advice for you, just offering support in a difficult situation. I would hope that they would be more sensitive to your request. Your little girl sounds so mature, I can tell you have done such a good job about explaining your illness to her without it being scary.
I wish I had more to offer here...
Cathy
Cathy