Eeek... please don't try friendship training. It may work for some, and that's great, but since you are new to horses and this one has already proven dangerous, she needs a VERY firm hand. Friendship training does not offer this.
Arrowsaway, I understand your concern but I think you misunderstand what FT does. It teaches a horse what is not acceptable (as kicking clearly is not).
It is not about just being friends with a horse, but about removing unnecessary stress and improving communication between horse and human so these accidents don't occur. The primary consideration is always the safety of both the human and the horse. There is a rather stringent application program and people are not accepted into the program if the instructor thinks that the circumstances are such that the person and horse won't benefit.
The lady has had the horse for three years, I had only been around horses about 18 months when I started FT with my gelding. It has helped to turn around extremely aggressive horses - one member had a very dominant and aggressive TB gelding that had almost killed a friend and had kicked her in the head; she was advised to have the horse put down. Now people comment on how trusting he is. Another lady whose story comes to mind has a mare everyone else was afraid of - she would literally attack with no provocation. She is now becoming a trusted friend.
FT does help to set boundaries with the horse - my gelding had been biting at me and becoming more dominant with me before FT, that has all changed.
He is an extremely stubborn and strong minded horse and I was not a confident person before this, yet it is helping us enormously.
That the mare has not done well with three trainers might just mean they all used the same inappropriate methods with her.
If the lady has stuck with the mare for 3 years she clearly cares for her, and has nothing to lose from at least checking out the FT website or joining the Yahoo Group and talking with the other members there (most of whom have done FT) about their experiences.
I understand scepticism about the program - it is indeed a very different approach - perhaps that is why it is so effective in difficult circumstances, as this one sounds to be.