Disconnecting the console from the internet is the only sure way to prevent player invasions in Dark Souls 2.
That said, there are many conditions for both being able to invade and being susceptible to invasions, so your friend shouldn't have to worry too much. In my 72 hours of playing the game, I've been invaded only 3 times, not counting the areas belonging to the PvP-covenants. Those are entirely optional.
Like the comments above mention, you can minimize invasions while online for about an hour by burning a human effigy at a bonfire. The item description for the human effigy mentions this effect:
A warm, soft, shadow-like effigy. Use this item to reverse Hollowing.
It also weakens the links to other worlds, preventing invasions and
most cooperation. Peer closely at an effigy, and one begins to
perceive a human form, but whose form it takes depends on the person
looking. #
The Way of Blue supposedly summons available members of the Blue Sentinels covenant to help the Way of Blue player being invaded. I don't believe it matters whether the Way of Blue player is hollow or not, but the Blue Sentinel must be human, wearing the ring and also not fighting a boss or near a boss gate. With all these conditions, I'm not surprised people have seen few protectors these first few weeks after the game is out. Only a portion of players elect to join the Blue Sentinels, and then they both have to sacrifice a ring slot and not lose their humanity to be able to help.
Since your comment mentions the original Dark Souls, I'll add that in that game you would never be invaded if hollow; only in human form. So you could easily play through the whole game without disconnecting your console and never be invaded.
In my experience, invasions have resulted some of the most nerve-wrecking and adrenaline-filled battles in the Souls series. They've also been some of the most memorable, so I recommend not trying to prevent them.
The ghosts are in fact real time, look at this video for evidence of this. I have also been able to communicate through the emotes with a ghost before (or maybe it was just a freaky coincidence)
Note This is Dark Souls 1 but like the other people have stated I don't see why they would change things.
Best Answer
There are NPCs that won't attack you unless you do enough damage to them for them to turn hostile. The only area I think we could call "civil" is the Firekeepers' hut in the beginning of the game and the town of Majula, where most friendly NPCs gather after you encounter them in the wild.
Like in the last game the people/monsters you meet are undead like you, and most of them have gone mad and will attack on sight.