My best friend has a friend who is dieing. Now she is closed off, please help?!?

[Chonic]

Well for awhile now my best friend has been very closed off ignoreing my phone calls, and telling my other friend that she does not want to be friend with us, because we will just end up pushing her away. He told her we would never and haven't, and she was just all like "yeah right" etc; so we have tried to give her space, we really have, but it's hurting to know she doesn't want to be friends with us anymore. Iv'e been friends with her longer then my other friend has by the way I'm in 10th grade, and Iv'e know her since 2nd. So yeah...
Well anyway, me and my friend have just found out that our friend who is being closed off, has a good friend who is dieing of canser. I guess she just doesn't want to be friends with us because she is scared that she will loose us too. So any ideas of what we can do to get her to relize we won't be leaveing her anytime soon, we tried giveing her space, but that made things worse. And this is really takeing a toll on all three of us over all.