What does it signify: someone constantly closes their eyes while talking, particularly in a heated discussion?

I have a female friend that closes her eyes constantly while speaking. What do you think it signifies? She is kind of spacey and I wonder if it could be to avoid any visual distractions or is this a sign that she is truly spacey? I would appreciate any thoughts as I am truly puzzled at this constant behavior. Even when she is upset she will close here eyes when speaking even to answer or to raise a point.