Re: USB key
Conceptually easily done, but I wish you hadn't gone into such detail, as I am not sure I'm comfortable advising on Linux by stealth. Could your friend not just have a frank conversation with her family, lay out her (very good) reasons for wanting to try it, and get where she wants by concensus? Here are the dangers:
1. She is talking about repartitioning. Always a dangerous exercise.
2. The partition will be visible to all Windows users who have at least an inkling of system knowledge.
3. Her "stealth" partition could very well set off Windows anti-malware alarm which is notorious for crying wolf when Linux is detected.
4. If she gets caught, it's a thousand times more serious in terms of relationship with her family.
This is life-advice and not technical advice, I know, but someone has to say it.
Newb: How far must I jump to clear the ledge halfway down?
Guru: It's bad to jump off cliffs. Let's look at better options.
Newb: Stop harping about "best practices" and just let me jump.