PS4: How to choose response in optional conversations?

I just got to Val Royeaux and Cassandra makes a remark; There is a greyed-out converstation wheel but I can't figure out how to access the choices and choose. When I try to talk to her by moving towards her and pressing X, it just closes the optional wheel and the conversation moves on. I have pressed every combination of buttons and can not figure out how to choose it. For past optional conversations, all I had to do was talk to the person who spoke and the wheel would become white and allow me to choose the answer. However, in this case moving closes the wheel. So how do you choose an answer?