Update:
So I decided against telling since, as most people mentioned, there is no point. Got a message from her saying to delete everything and not tell anyone about us, I replied and told her that I wouldn't say anything but she should tell him because I would want to know.
She did, then gave him my number which was a super fun phone call. As we all suspected I was the one to blame! Lucky i'm moving house shortly!
So I decided against telling since, as most people mentioned, there is no point. Got a message from her saying to delete everything and not tell anyone about us, I replied and told her that I wouldn't say anything but she should tell him because I would want to know.
She did, then gave him my number which was a super fun phone call. As we all suspected I was the one to blame! Lucky i'm moving house shortly!