Earlier today, before entering the room, Theodore had gone to see his followers. He wanted someone to observe each and every move of Lillian because she was growing stronger by the day. She was becoming a larger threat to the people of Palace, especially to the Princess.
And he needed to know what evil she was cooking up so that he could protect his love from the possible danger.
However, he was making this task of protecting the Princess from the witch harder for himself by not telling the Princess what Lillian was doing exactly. If he had just been truthful with her and told her that Lillian had been summoning mystical beings inside the Palace, then Adeline would have been more cautious.