I had this happen on a playthrough that I a had reached the party for. Originally thought it was my rep with her since that round it had dived. But through a couple other profiles, I was able to repeat it anytime I finish the patrol quest and then removed her from my active party. I then get one last chance to talk to her (If I don't sleep or leave camp). Once she freezes I can't start the party, and some companion quest are prevented from completing.
I have only completed the patrol quest peacefully so I'm not sure if this happens if a battle breaks out, or if you keep her in your party longer. I'm reporting it as a bug today.
