If you can do this quietly (better to get it lined up before saying anything) - find out what her daughters "dream" is..travel to Disney World....meet Hanna Montana....whatever....

then contact the closest chapter of "make-a-wish foundation" and tell them the prognosis.... they make things happen, and might be able to bring some great smiling memories for both of them...they did for our family 20 years ago...

good luck