okay...first, i think that she is the one that Klaus & Elijah love, remember when Elijah saw the resemblance on Katerina? yup. And when Klaus a dit that l’amour is a vampire's greatest weakness, Elijah told him that he cared ones....uhm, Charlotte. Second, i think that she is NOT a doppelganger! she is the original petrova, katherine is the first petrova doppelganger & well...Elena is the second. Third, i think when she comes...probably on season 3, she might also montrer Catelle (probably kat's sister) and then we'll found out plus about the petrova family when TVD returns....my opinions =D let me know what u think?