Does anyone know how to edit this?
The UI is slightly confusing, because it re-uses the label "Dialogue name" to refer to two different things.
On the Custom tab, the Dialogue name field defines
the name of the player or player character, which will be spoken by the girl during dialogue lines. Editing this field will achieve the desired effect.
On the Modding tab, the Dialogue name field defines
a descriptive title for the dialogue file, such as "Sexy Cheerleader version 3.1". Editing this field won't alter the game's behavior.