Why are so many people recommending Portal? As others have mentioned, that is a horrible idea. She'll have enough trouble navigating a 3D environment as it is; add portal mechanics to that and you'll have a huge problem. But if you're really set on Portal, you should at least show her Portal: The Flash Version first.
Anyway, I would start with a 2D game. My first suggestion is Canabalt. It's free and only has one button. The main problem is that it's impossible to win. If she got upset over getting stuck in a trench, I don't think she would like crashing repeatedly into walls.
I also recently completed the 2D, free game Cave Story, and I enjoyed it. It gets kind of hard at times, though, and it starts out in a cave with spikes to jump over. On the other hand, if you start her out on Canabalt she'll have some solid 2D jumping skills to get through those problems.
You could also show her a 3D game that has no enemies, goals, or puzzles. Unfortunately, the only examples I can think of offhand are The Path and Dear Esther, and neither is free. Also, both of those are kind of creepy. But if you can find a mod or something that will turn a game that you already have into a happy fairy land, go with that. Build up her confidence with the controls before asking her to do something difficult.
Anyway, I would start with a 2D game. My first suggestion is Canabalt. It's free and only has one button. The main problem is that it's impossible to win. If she got upset over getting stuck in a trench, I don't think she would like crashing repeatedly into walls.
I also recently completed the 2D, free game Cave Story, and I enjoyed it. It gets kind of hard at times, though, and it starts out in a cave with spikes to jump over. On the other hand, if you start her out on Canabalt she'll have some solid 2D jumping skills to get through those problems.
You could also show her a 3D game that has no enemies, goals, or puzzles. Unfortunately, the only examples I can think of offhand are The Path and Dear Esther, and neither is free. Also, both of those are kind of creepy. But if you can find a mod or something that will turn a game that you already have into a happy fairy land, go with that. Build up her confidence with the controls before asking her to do something difficult.