Billy Trump knows Nick is a Grimm. She also knows Sean is a zauaberbiest. Watching Lucien it seems Billy did not tell him any of that. Then maybe she did that is why they targeted Sean for political office. Lets not forget, no matter what we think about how Sean has been on the side of good, helping the scooby's. He is still a zauberbiest, given the right incentive his biest will kick in. The same with Adalind, she can work at being good as hard as she wants, she is still a hexenbiest. The right trigger she is off and running. in spite of all the good will she has built up. That is what she seems to be afraid of. We know Adalind and Sean have an involved meeting. (they where on set together during the 100th viewing). The out takes show Kelly is still in tow. So he stays till the end. How the dynamics will work, maybe this is the Juliette turning to Sean moment for Adalind this time. Because Nick is being unreasonable again.
Embrace your inner Biest..... We all have one