It’s tough to respond critically to a piece of writing that it so personal. Nevertheless, with respect:
For people with Alzheimers, early memories are often the strongest and most reliable. It’s possible that someone from her past engaged reliable memories and feelings in a way that you or your mother could not. It might be less about needing a man per se and more about needing someone who can remember what she can manage to remember and share that positive experience with her. That she would miss his company and care to the point of devastation is understandable; she has returned to the darkness of her lonely battle with losing her mind.
The story of your grandmother is poignant and well-written, as is the message of the rest of the piece. However, I think by connecting the two you misjudge your grandmother.