"his only response is to stare blankly through her -- almost with an inquisitive type of expression. I know that sounds crazy, but it's truly the only way I can think to describe it."
This does not surprise me at all. You need to listen to her and agree with her that it is not normal and appears to be unkind, but then remind her that it is not intentional and that he cannot understand what is needed. She will still be hurt most likely. I said to my girls "If your Dad was in a wheel chair you would not expect him to play soccer with you, there are some things that your Dad struggles with, he can't help it" Then I point out the things he does do well. Adolescence was the worst time, too much emotion.