The Identity of "A" Was Finally Revealed in the "PLL: Original Sin" Season Finale

On more than one occasion, the show hints that Kelly lives in Karen's shadow, even dressing up as Karen to do her bidding at one point or staring just a tad bit too long at a photo where Karen and Imogen are cuddled up close while she's off to the side. Could she resent her sister for outshining her? Considering Kelly was attacked by "A" in episode six, it became clear she wasn't "A" either.