I was just talking to Rach and she said that Halo gives her headaches too. Obviously, Rach can play Mass Effect for hours on end without headache. It’s worth noting that Mass Effect is not a first person shooter, per se, it’s an over the shoulder shooter. And, if watching FFXIII didn’t give you a headache, there’s no reason Mass Effect should.
Added bonus: you will be controlling the camera on a console, not Holly, so one hopes you won’t get motion sick. And, I mean, it’s not like Holly had marvelous control of the game anyway :P
TL;DR: Helena, give Mass Effect a shot because it’s fucking worth it. IT’s like driving.