As it often happens, when a beloved person dies like your grandmother, the loss of physical presence of that person, creates a longing and emptiness, such as you have experienced. To fill that empty space in your heart, you seek to be comforted. This unconscious request invites an entity (soul that hasn't moved into the light at the time of death) that has such an effect. However, having an entity in your body separate from your own soul has a weakening and disorienting effect. I am not getting that the entity is your grandmother. Your grandmother has made a good transion and appears to be doing very well. She may be ready to speak with you if you so wish, tell you about her experiences and her new, exciting life (non-physical) and journeys.
Regarding the removal of an entity, I can help you do that during a telephone session of Sacred Santemony (see my website).