The weekend before last was a music festival here called Osheaga; went with a group of 5 of us. I knew 2 pretty well but there was a friend of a friend who has/had a thing for me and won't let it drop.
She wouldn't leave me be and at first I tried to just avoid her (having already made my intentions clear that I wasn't interested). Cue late evening after I start chatting to some Americans, 2 guys & 2 girls and she again interrupts awkwardly and tries to engage me in 1-2-1 conversation. I call her out in her continued "clingy" pursuit of me which she denies, calls me an asshole and storms off. I apologised to our group for putting a bump in their evening and went off to do my own thing... it put me in a low mood but I felt a little more me.

I think I needed to be a little more clear in my intentions when I first told her. I was polite/diplomatic which I am unsure may have given her hope. I didn't want to be an arsehole about it but in the end I felt I didn't really have an option