You are interpreting this quite correctly; it is an example and a quite clear one, of spirit possession. It is certainly possible for the mind to fragment, and this is well-established by a psychologist in describing the peculiar, real nature of Dissociative Identity Disorder, formerly known as Multiple Personality Disorder, where more than one personality can be created within an individual and take on differing characteristics and have its own knowledge, including such things as language preferences and even gender, but that was not the case with this Indian woman. This was indeed a case of spirit possession, and it was aided and abetted by the woman herself carrying out extensive meditation without setting up any safety procedures to request divine protection against any intrusive energies, particularly other consciousness. There are many lower order beings who are invisible to the eye but present all around you, and they can invade your energy under the right conditions and take up residence within your energy field and, given the right state of consciousness, may well move into the foreground and take control of the body for a time, being able to speak or carry out physical activities as well, just as happens with Dissociative Identity Disorder.
But in this case, it is not a subcomponent of Uttara's mind being described in the persona of Sharada as the Bengali woman who emerged from within her, it was the spirit of Sharada that was attracted to her energy and it was the meditation that allowed Sharada to gain a foothold and penetrate her auric field and attach, and remain within Uttara's energy henceforth. The spirit, indeed, had been in limbo and was truly lost. There was enough affinity between the two to provide an attraction of energies, and this ended up saving Sharada, with respect to being lost in the dark, at least in giving her a place to reside that was more familiar and even gave voice to her story. This could have been prevented if Uttara had simply prayed to the Almighty for protection from any intrusions, and that would have prevented the spirit attachment from taking place.
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