I've got the same problem. I had Lae'zel in my party when we met and fought the Githyanki in the pass. Afterwards I had her leave my party and added Wyll. At some point after that, I could no longer speak to her at all. I tried to kill her, which aggro'd Shadowheart so I had to kill them both. Couldn't rez either of them with the scrolls, and the lich guy wouldn't help me either so I had to reload that save.
I got the scene where we all get sick and she tries to kill us, but aside from that I haven't been able to speak to her at all, including when she has an exclamation point above her head.
More recently, I got the scene where everyone had the sexy mindflayer dreams and got new powers. While talking with everyone (except Lae'zel) about it, I tried to persuade Astarion to tell me about his dream. I failed the roll and he ended the conversation. After that I couldn't initiate conversation with him either. He's still in my party and I still get the text box when I hover over him, but I can't talk to him at all.