trine. It's pretty forgiving, looks pretty, and introduces multiple gameplay elements, include RPG skills with upgrades, minor equipment management, puzzle-solving, range-based combat, melee combat, and how to develop different strategies for different enemies.
Also:
The Longest Journey is an oldie but definitely a goodie. It's a point-and-click adventure game with dialog options, a strong narrative, and puzzle solving. If you get stuck, there are Gamefaqs walkthroughs to help get through some of the more difficult brain-twister puzzles.
You might consider playing co-op games (online, LAN, side-by-side, etc.) so that you can help demonstrate by example and also avoid the "backseat driver" role.
Example: Titan Quest. Also consider offering games that have an "easy mode" or are very forgiving (ability to save and reload without losing much progress, no lives/infinite lives).
Other games I could recommend:
Okami - simple and straightforward controls with a lot of gameplay variety and a fantastic story. Minor RPG aspects (attributes), 3 weapon varieties, and minor inventory management.
Patapon 2 - has a very forgiving "easy" mode; in general the game is extremely forgiving if you fail a mission.
God of War - easy mode is very forgiving, game is pretty forgiving if you "die" (you just restart from the last check point, no penalty), combat isn't too complicated (as compared to, say, many of the pure-fighter games with oodles of combos)
Dog's Life - non-combat game. Mainly puzzle solving, exploration, and some mini-games. Fairly up-beat and straightforward, but nonetheless entertaining.
Tomb Raider: Legend - camera isn't too bad, the game is fairly forgiving, and the dialog is entertaining. Platforming and puzzle-solving are way less frustrating than TR: Anniversary.
Primal - another female protagonist, yay! relatively "simple" combat, the main focus is puzzle-solving with the two main characters, Jen and Scree. Also, shapeshifting is awesome - I have yet to find a game (and I have looked and tried, trust me) that handles shapeshifting as good as this. The game is moderately forgiving, from what I can recall - I don't remember having too much trouble staying alive.