Build and Runes
Attack speed reduction is extremely strong against Irelia, which lessens the effectiveness of her Hiten Style’s active.
Be wary of having higher health than she does, as her Equilibrium Strike will stun you instead of slowing you.
Be wary of being near low-health minions as she can dash on them to get closer to you.
If you know her animation for her hiten style, you can time it for 5 seconds and engage while its down, for it no longer does true damage but only do so if you can kill her and are tanky enough for it.
Irelia is a very mobile Bruiser with insane dueling capabilities. Her damage revolves around basic attacks, however reducing her Attack Damage is not an option because of her Hiten Style active. Try reducing her attack speed instead.