You suck it the hell up. I'm sorry if that sounds insensitive, but that's just the way it is. The woman has cancer, she does not need to deal with comforting you for her illness.

My mother died in July. My older brother could never put her well being and her emotions above his own, so he just came by and cried a lot. She didn't want him to visit because of it, it made her sad(der) and tired(er). But then again, she couldn't tell him not to visit, because that would hurt his feelings.

So, that's not really a tip. But suck it up.

For me, I focused on everything else. My mother, and your friend, and everyone else, is not their disease. They still enjoy the things they used to, they still care about how you are doing and what's new in your life. They will still watch bad tv-shows, still think Johnny Depp is hot, still love roses and.. whatever else that always made them them. Remember that, cut that persons hair, not the cancer patients.