My sister is currently deployed with the navy on a ship for 8 months. She would really like to have fallout 4 for her PC. Is there a version for military personnel that doesn't require internet access?

Thanks in advance!

If she install the game before going to her assignement, you don't need to be online to play.

Just start steam in offline mode and play

It still has to phone home occasionally to Steam though, I think.
Not sure how it works but it does HAVE to go online to allow you to keep playing.
Every couple weeks?

No, only if you want updates for your game.

If you install games (single player) on your pc with an internet connection and you got o a location were there is no network, you can still play, no more connection is required.

PS: the game saves will not sync with your steam cloud thats all