two elderly ladies rooming together at a nursing home becomes best friends regardless of their odd personalities.

>>>>Is either one of the women more of a central character?

It's the story of a relationship, an Odd Couple match up.? ?I don't think it's necessary to tag one of them as the central character. At the center of the plot is a relationship, not a particular character.

Is either one of the women more of a central character? Which one experiences the most amount of change throughout the course of the story?

As above, they said it well without having more info on the struggle.

Story is conflict, you have given us no conflict

You should show that they become friends rather than tells.

What events does the story tell that shows is their growing friendship.

Example

Two woman completely different forge a friendship during their battle with their nursing home owner over respect and treatment of the old.