[ She lifts an eyebrow at her, knowing reacting the same way isn't going to get them anywhere, but while she understands her anger and pain, she doesn't think it's justified. ]

Yes, it is. If you did it, in full awareness of your actions, if that's what you really wanted to do to him, then by all means, beat yourself up for being the sort of scum who wouldn't think twice before stabbing a friend in the back.