[He knew she would apologize first, so there's something of a sigh as he briefly closes his eyes.]

Even so, I was fully aware of the situation and should have pushed harder to stop it from escalating. So I also I owe you an apology.

[He is not going to let her take all the blame, just like she wouldn't let him do the same. It takes two people, and if anything he feels a bit more responsible given that he had been more sober and aware of her identity at first. That said he also knows that she will still feel responsible so he won't try and push it. Just take responsibility for his own actions.]