The first thing Jack did was direct his senses to his back. Probably the woman was talking to someone behind him who just happened to enter this room.
But after sweeping his consciousness throughout the room, there was only this woman. Jack returned his attention to this woman, who was still staring at where he was floating. Her next words convinced Jack that she was indeed aware of Jack's presence.
"You are… an outworlder… How do you get into this spirit form?"
Jack wanted to reply but he couldn't. He wasn't able to speak during his incorporeal state.
The woman seemed to understand Jack's dilemma. She said, "You can focus on the message you want to convey in your mind. I will be able to hear your thoughts."
Jack did what the woman told him. He didn't sense any malice in her. Plus, she was also a captive. Jack focused hard using his mind and directed a thought at her, "HI, HELLO! CAN YOU HEAR ME?!"