My girlfriend refuses to take accountability for a mistake she made and now I don’t know how to move forward

My girlfriend and I had plans to go to an event that was really important to me. I asked her multiple times during the week if she had confirmed everything on her side, and every time she told me, i should not worry But then im pretty sure you know what happened next the good ol' not doing NOTHING. Now she is putting the blame on me and says things like I should’ve reminded her again or I shouldn’t make such a big deal out of it and I was putting too much pressure on her. Idk what to do man how do i get her to Be ACCOUNTABLE for her actions.