I think the most important thing is to throw away the guilt. My mother was diagnosed with cancer many years ago, and she wanted to keep things private. She only asked me once for support. People deal with a cancer diagnosis in different ways. I wanted to help but I could do nothing but respect her choice to not allow it. I have cancer myself now, and although I am open about it, I have children your age and I won't shut them out, but I do shield them a little. I want them to live their lives, I'm not their problem, but neither am I closed off to what they need from me. I would say tell her you're there for her, check in regularly, and if you feel you need to travel that 500 miles, do it. For you. Ask her what she needs. Don't let the subject of cancer be taboo. It's a horrible situation, but like me she's probably supported by nearby family and by medical professionals like Macmillan nurses. None of us know how the journey will end but we try to stay positive. Just show her you care by phone and text. I can't speak for her, but that would be, and is, enough for me x