Please go to your GP and don't give up on the counselling. You had one session, of course the person was going to be a stranger to you!
Why do you care if she fails her dissertation? She is not your problem anymore - and never really was, to be quite frank. You're treating this as if it was a breakup; it wasn't a breakup. Friendships come and go and you need to accept that, otherwise you're going to be suffering in self pity for a long time yet.