If you can set up a situation where the liklihood is that she
will offer her squeal and kick, you will be able to better anticipate it and
react immediately (which is key).
No sooner than she offers,I would shout NO!! (or
you use when letting her know that the action is unacceptable)
while turning her in a a few very tight circles, or
backing up, but catch her off guard and makee the experience
as uncomfortable as possible for her.
Then ride on. Again, let the situation again tempt her and be
ready to make her actions totally uncomfortable for her. The important thing is
that you must be able to react immediately. Shouldn't take more than a few
Lacking a friend or buddy to ride with, when you are riding in
a group, try to react as soon as you realize what is happening.
I have had a couple of horses who were made uncomfortable when
approached too close from behind and this method was most successful with both
of them. I think that what also helps is riding in group situations as often as
you can so that the horse comes to accept that this is a safe situation and that
the other horses are not going to harm her either.