EDIT: The only times Agrias interacts with Gafgarion are this interaction, right at chapter one when they're both protecting the princess (and so the betrayal part means it wouldn't be then) and at the execution site (where Delita has long-since left with the princess ages ago)

This new interaction happens at the castle gates where Ramza and Gafgarion have their duel inside. Agrias is standing outside when she has this lengthy conversation.