Writes Ausiello, "Vandervoort—who left the show at the end of season 7 only to return briefly the following fall to wrap up Supergirl’s story—will be back for one episode (tentatively scheduled to air in October).
"Smallville" and "V" are both produced by Warner Bros. It’s safe to say the actress’ comeback was signed off faster than a speeding bullet."
In the same piece he mentions that Vandervoort joins John Schneider as former cast members making guest appearances this coming year.