Silver Fox's identity is rather open at the moment. Originally, Wolverine and Sabretooth remembered Creed killing her decades ago. She returned, alive and well, in Wolverine (2nd series) #49, pointing out her death as a false memory implant. She died again in #64 at Creed's claws but, after Logan regained his full true memories after House of M, it seems she really did die back in the cabin. So who the Hydra operative was is uncertain.