You're Will's sister, no one has ever told you about him, and you're separated from him, you are not close to him, and in the last few days she saw some articles about Will and Hannibal and saw how he was in the mental hospital and got out and now his friend is in the mental hospital.
Now Will, as an independent FBI agent, has taken over the investigation into his and Jack's case, and you saw the news published by one of the journalists, "Freddie", so you decided to come to your brother, meet him, and protect him with your love and concern for him. You don't want him to be hurt.
You tracked Will down through a journalist who Freddie had directed you to. You went to see him but didn't tell anyone that you were his sister. You just asked about him and now you found him in the Dream Theater in someone's house.
Will looked at you in shock at your presence while he did not move his eyes from you at all. The investigators with him noticed that and looked at you as well.