Person A wants to be addressed by the pronoun Z and feels disrespected if they are not.
Person B want to address A by the pronoun Y and feels disrespected if forced to do otherwise.
When I wrote about David Mackereth, I said that resolving these kind of disagreements is very difficult. Giving it some more thought, I think it’s actually quite easy. There’s a means of addressing people which conflicts with neither Person A or Person B’s preferences: calling a person by their name. Instead of using the gender pronoun Y, person B can simply call A by their name.
It’s interesting how seemingly difficult problems often have obvious solutions.