horse had mounting scare

Question
i am looking after a 12yr old 15.2hh,who the owner tells me had a mounting scare which was there before but the owner got rid of it and now its back,she doesnt buck or rear but when you go to mount her she moves her bum around in a circle so if your in midmount you pretty much have to jump off,how can i fix this

Answer
Hi Suzie,
  I would just like to say at the outset, that your safety is the primary consideration, so any suggestions I make should be considered in that light.
  It might be helpful to know the nature of the original scare, and why it re-emerged after an apparent "cure". The other question is the direction in which she moves her quarters.
  The first port of call with many "horsey" issues is, self examination. Check to see that your rein grip is not a contributory factor. I don't know how athletic you are, but obviously the quicker and lighter you can be the better.
  It would be a big help if you had somebody to act as an assistant. If the mare moves her quarters away from you, consider lining her up alongside a wall or fence to limit her scope for movement. I wouldn't recommend a mounting block as you are only giving yourself something to fall off, but I would let down the nearside stirrup as much as possible. Then using my hand I would put some weight on the stirrup, and watch for a reaction. If she stands still remove the pressure immediately, and make much of her. If she moves try to increase the pressure and keep it on until she stops, then remove the pressure and pat her. The basic message here is that she gets rewarded for standing still, and penalised for moving. I would keep repeating this exercise as long as she keeps moving(patience really can be a virtue).
  The next step really should be done with the help of an assistant, and alongside a fence. The helper holds the horse and you put your foot in the stirrup and lift yourself up,but don't complete the mount. If the horse fidgets try to hold your position until she stops, then dismount and make a fuss of her. If she stands still dismount immediately. If you can reach the stage of performing this manoeuvre 3 times in succession without her moving, then complete the mounting.
  Well this turned out to be a rather longwinded answer, but I hope it helps, and I would love to know how you get on.
                       Regards,
                              Brendan
P.S. It might take a few sessions to really cure her.