Pretending to pay attention

I'll spare the details and get to the point ... my ADD wife has heard enough times that she doesn't pay attention, doesn't listen, talks over people, etc and she gets that.  However, her strategy now is to "pretend to pay attention."  She'll be watching tv and on the computer and I'll talk to her and she won't look up from her computer or tv (whatever has her attention at that moment) and then when I have finished talking, she'll reply with an inappropriate response or an inappropriate facial expression (in the past she'd simply stay in whatever zone she was in).  When I say, "did you hear me correctly?" she'll repeat what I've said back to me word for word and then try to defend her inappropriate response.  This doesn't happen every time.  Sometimes when I say the "punch line" again, she realizes her first response was inappropriate and then is in the moment with me.  This is happening more and more and it makes me feel lonely.  One reason I feel lonely or insignificant is that I know she would never treat someone else this way, she'd give them her undivided attention.  How do I get around this behavior?