I work at a riding school (have namechanged to avoid outing said school) and this morning was asked to give a private lesson to a 33 year old woman. Naturally as she is a beginner I chose her a quiet, calm yard horse, naturally a bit slow and sedate but more importantly, safe.
So she gets on the horse and immediately asks me "will I be cantering today?" I said "no, that is for when you become more advanced" and she replied "fucking hell" 
. So ignoring what I assumed to be a slip of the tongue I asked her to walk the horse around the school. She did this well and seemed pretty confident. All was ok until I asked her to trot - she kicked the horse and he didn't budge (as I said, he's slow!) and so I suggested she use her voice as well as her legs. Well, she immediately sprang into a tirade of insults - "Go on you bastard! fucking move you dopey c*nt, come on come on!! for fucking hells sake, fat bastard thing move your fat arse!! etc etc" all the time kicking softly so he could barely feel it. At one point I became paranoid that I was on some kind of hidden camera comedy show it was surreal. I told her to calm down and she replied that she was calm but "soppy bollocks here needs a rocket up his arse".
Anyway the lesson continued, she dismounted and to talk to her she seemed fine! well dressed, nice car (judgemental I know but to afford a car like that either she holds down a good job or her husband does at least!) so I just don't understand the outbursts.
AIBU to refuse to teach her next week despite the fact that she's asked specifically for me? she makes me uncomfortable.