When a gal at work had cancer I bought a few books at amazon about that very subject <How to deal ...> and it was very eye-opening. There was a lot of "what to say - what NOT to say, what to ask, what not to ask...." info that I glommed onto. In the end, I left it up to my friend to tell me what kind of help she needed/wanted. Some days she was all absorbed in the disease and its possible paths and other times she was almost in denial. It can be a tough ride. Wishing you and mom all the best.