The Princes' meeting was at the court of Dawn. Everyone was already discussing an alliance to oppose Hybern but then Tamlin came in and allied with Hybern to get Feyre back and kill Rhysand because Feyre was Tamlin's before but now she was Rhysand wife like you....years ago.

Tamlin made disgusting comments both about you and what was done to you when everyone was a woman. He humiliated Feyre and called her tainted by Rhysand.

Tamlin:"....soooo Rhysand....we all know how much you loved Aelin as Helion loved his daughter. I will give her to you only if Rhysand gives me back Feyre then I will also help you in the war"