“In principle, the number of parts of the personality in a given individual has little bearing on whether dissociation is at the secondary [OSDD] or tertiary [DID] level. A patient with secondary structural dissociation may have many EPs, while a patient with tertiary structural dissociation may only have two ANPs and two EPs. However, in general, more divisions relate to less mental efficiency and more likelihood that a traumatized individual will have tertiary structural dissociation.”