Percy Jackson's Twin Sister (The Lighting Thief)

Percy and Allison Jackson are about to be kicked out of boarding school... again. But that's the least of their troubles. Lately mythological monsters and the gods of Mount Olympus are coming into their lives. And worse, they've angered a few of them. Zeus's master lightning bolt has been stolen, they're the prime suspects.
Now the Jacksons and their friends have just ten days to and and return Zeus's stolen property and bring peace to a warring Mount Olympus. But to succeed in their quest, Allison and Percy will have to do more than catch the true thief: they must come to terms with their father who abandoned them; solve the riddle of the Oracle, which warns her of betrayal by a friend; and unravel a treachery more powerful than the gods themselves.
Allison is a sarcastic girl with an interesting life...

(All credits and ideas go to Rick Riordan for this incredible and spectacular series. I'm just putting my little twist on it.)