I'm a girl and I like games that are RPGs... Rune Factory is a really good game... I like it.
I tried Harvest Moon Cute, and it was kind of strange to me.... I didn't like the controls at all.
There is a really good Rune Factory community on the net, here is the link incase she wants to play it, with a complete guide throughout the game with maps and extras within the game.
Click Here
A game I am playing right now is Super Princess Peach, it's a mario game, but for girls. It's really fun, and I even know a couple guys who like the game too because it's mario.
I also like Final Fantasy III, and Final Fantasy Chronicles: The Ring of Fates
Nintendogs is fun as well, and I know a couple guys who like that game too, so it's not just for girls!
Let's see... What else?
I like a game called Trace Memory, it's about a 14 year old girl who has to find her father on a cursed island and it's about finding the clues, etc.
I also really like a games called Professor Layton and the Curious Village.
Big Brain Academy is fun as well... I let my Grandma play that game and she had a lot of fun.
It's just trial and error... I've gotten games that I thought looked really good, and they were horrific crap... So, just ask her some questions of what she thinks she might like and try to make some decisions on what you think she'd like.
You can always change it out later if there are games she doesn't care for.
I hope she likes it!