This answer contains spoilers… (view spoiler)[I would say no - This is very heavy on the romance. While there's nothing explicit, there's a lot of kissing, touching, romantic looks, etc, that might not be appropriate for a 9 year old. There is one sex scene, but most of the action is implied. I personally would not let my 9 year old daughter read it. (hide spoiler)]
Ada I don't think it would be much fun for her, because, as Lorna already stated, there is a lot of romance in it. But I would definitely recommend her to read The Scorpio Races. It's also by Maggie Stiefvater, but much more exciting and it contains almost no romance. :) Hope I could help.
Andreanna I would say no. It has a lot of romance, but when she becomes a teen I would recommend it.