She actually didn't see him ~ no one does. This has a lot to do with the way the eyes work, how motion is perceived and analyzed in the brain, and relative speed, etc.
Nothing any of us can do about it. DUI, however, is a matter of choice.
I'm a little confused by this story. So you have a two lane road, presumably one eastbound lane and one westbound lane. Your friend was traveling east. The truck was on the otherside (the westbound lane?) traveling west. Why would she decide she really needed to be in the other lane? That makes little sense. Regardless of oncoming traffic being visible or not, she violated the rules of the road.
Someone sober who finds it acceptable to drive on the wrong side of the road is a hell of a lot more dangerous than a social drinker slightly above the limit driving home following the rules of the road. But I'm sure she didn't receive anywhere near the punishment as someone stopped at a DUI check point that didn't kill anyone. Afterall, it was just an accident she was driving on the wrong side of the road and as long as she wasn't drinking, that's okay.
BTW I have superhuman abilities. I can actually detect motorcycles.
Oh, and my other superpower is yes, I actually can understand Cannibal Corpse lyrics.