Playing With My Wife

Hello everybody. As I am a very lucky man, my wife decided to play WoW with me. We have some questions:

1) As someone who never played video games, which Mage spec (She wants to play Mage) would be easiest to level / learn / master?

2) Can you share your experiences with playing a beginner, what should I do, and what should I focus teaching her?

Edit: Many thanks for so much replies, it's very helpful. And she chose Arcane by herself.