Are you going to play the game together, or will she be playing it completely by herself?

If the first, I would actually suggest FFVIII personally. It's easy to get into and is very newbie-friendly as soon as you actually do get the hang of the Junctioning system. The only problem though, is the complexity of the Junction system at first. But if she gets some additional help in learning it, I think FFVIII can be a great choice. Most of the FF-playing girls I know (who aren't hardcore gamers/been gaming for many years) has prefered FFVIII over many others in the series.

If not that, though, I'd absolutely say FFIX.