I would skip the 3D worlds for now. Save FPS for 'Games 201'. If you're having to show her how to hold a controller- then I would scale it back a bit. Give her a top-down view game or a sidescroller. Even something simple like Peggle would let her get used to using her thumbs on the sticks. As much bull that gets bandied about, casual games are really good for getting newbies used to the controls. Pick a game that's untimed (no stress) and doesn't use fast twitch- keep it low key but interesting.
I would go for Peggle, LBP, Arcade classics she'd know but are now on XBLA/PSN (let's say...Galaga or Ms Pacman), Katamari games. There's a really fun game we played yesterday that would be good for getting her used to gaming- Sumo Squash. Basically, you each get a sumo dude and try to squash the other person. It moves (so not too boring) but only has two or three buttons that need mashing so it shouldn't be too overwhelming.
I also agree- find out what she likes and go from there.
I would go for Peggle, LBP, Arcade classics she'd know but are now on XBLA/PSN (let's say...Galaga or Ms Pacman), Katamari games. There's a really fun game we played yesterday that would be good for getting her used to gaming- Sumo Squash. Basically, you each get a sumo dude and try to squash the other person. It moves (so not too boring) but only has two or three buttons that need mashing so it shouldn't be too overwhelming.
I also agree- find out what she likes and go from there.