You can charge your Q on your own low health minions forcing her to either get the minon(s) but get hit by your Q or she will miss the minion(s).
I would recommend taking Grasp or Glacial Augment against Irelia and rushing Bramble Vest and Plated Steelcaps. You need to be very careful in this matchup, especially early game. He's going to try to auto attack you then E away very often, even under your tower.