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I've read this book along with the series of I'm sure went up to about 3 or more other books. I read them around the year 2008 or 09, I can't remember most of the story because I was young but I loved it.
The book cover showed a little girl maybe the age of 11 to maybe early teens holding/cupping a green stone that I think could give her the ability to talk to animals or do some sort of ability.
I vaguely remember bits and pieces of the story but someone else was after the stone which sent her on an adventure to get the stone to right place out of the reach of the wrong hands. I think she had a younger brother with her or a town friend that joined her on her quest. I think her father or guardian was a teacher or a scientist that faked his death before the quest because he knew she needed that comfort of him being out of danger while she went out. He knew she had something that was special that effected the stone. (From book 1)
I could be incorrect about some of the details, it has been nearly 10 years since I've read them.