Hey Doc K

My recommendation is that you browse thru the "Don't you just hate it" thread on the Coping/anger forum to get a quick overview of many of the things that irk cancer patients. Many of them won't apply to you, but sometimes well meaning family members fumbling attempts at reassurance hurt the most - for starters don't tell her "this will all be for the best" or minimize this tragedy (at her age with a 2 yr old son, this is dramatic and not a comedy).
In a bit of serendipity, I just ran across a book: Help Me Live (20 things people with cancer want you to know) that has an excellent appendices that read as though cribbed from this site.
[please use the Amazon link on the OCF forum if you buy it}
Finally, be sure to keep in touch and volunteer to do something specific. It's really not very helpful to offer a generic "If there's anything I can do.." as that places the burden on your sister. It's difficult being in different states so I agree with DavidCPA on getting your sister to join up here at OCF so she will have a virtual support group.
Charm