Your mom is the only female character in the game you can’t romance.
The Affinity and Persona relationship still applies to Mom. For all intents and purposes, the game treats her the same as the male characters.
Mom starts with High Affinity and Nice Guy persona. How you handle the relationship will affect her attitude toward you. Want to bring a girl back to your room? Well, if Mom is not happy she might end up spoiling the mood.
Diana plays Mom in the game Mothers and Daughters.
Actors using their first name in productions is a common convention in adult and anthology storytelling. Mom is a character created specifically for this production, distinct from the fictional actress who portrays her.