Mordechai had told Esther that she can't reveal her nationality and Esther took that very seriously. Did he tell her that she was suddently allowed to reveal her nationality at the second party or did Esther decide that herself?
To clarify:I'm looking for an explicit source (Midrash, Gemara, etc.) that says that Mordechai told her she can tell her nationality at some point. There are numerous ways that she could have tried to get the king to change his mind without revealing her nationality if that had been necessary.