Parallelogram

the long version

"In a desperate move to save the life of her parallel self, Audie Masters managed to bend the laws of physics. But now she's trapped in the wrong universe, with no sign that her scheme to save her alterante self, the famous teenage explorer and adventurer Halli Markham, actually worked. Until she an sort out the physics of what went wrong, Audie has to pretend to be Halli - and fool everyone from Halli's parents to the guy who's in love with her. And meanwhile there's her own life Audie would like to reclaim, including Daniel, the only one who knows the truth about who she is"--Page 4 of cover.