We love this game in our house.
Be sure to get her the dance pad in addition to the game. Sometimes they come as a bundle. But buying the PS2 game by itself would not be good. Gotta have the pad. Preferably two, because you can "duel" against a friend. Much fun for a slumber party or play date. I got our pads on ebay for cheap, 2 years ago.
Keep in mind too that there are a number of DDR PS2 games out there--for example, we have the Disney one. It's a hoot. You dance with Donald, Mickey, etc. Britney Spears has one too, I think, though maybe it's a little too sexy for a 10-year-old!