I've never done it, but I've seen lots of videos of people doing it. In my opinion the TAP should only be used in extreme cases where everything else has been tried and the horse is going to hurt himself or others if something is not done about it. There are so many things that can be done to get a horse to be respectful, I think the TAP should be a last resort. I really don't know enough about how it works to form a proper opinion. I just know I was very disturbed by it the first time I saw it. It's hard to tell exactly what is going on.
Tell us a little about your filly. What are her issues? There might be other things you can do to fix it. If you are going to do the TAP, I suggest you consult with someone that has done it many times with success. Get the video made by the guy who developed the tap (Paul Williamson). I have not seen his instructional video so I can't speak for it's quality or content, but it would be best to learn from someone that knows. It seems like something that could very easily be done wrong.
For those that don't know what the TAP is, check out this website: Hybrid Horsemanship I am not for or against it at this time, I don't know enough about it, but I think it is important to be educated on the different methods out there.
From what I've seen of it, I don't think it could harm a horse (it's like 'twitching', you're releasing endorphines to relax and help him go down), but I certainly do not think it is for someone who is learning how to do it, so that they can do it for the benefit of their horse. If you think this is what your filly needs, I suggest you find someone in your area who knows how to do it; don't just learn how to do it, and try it on her because, it could go badly.
Even Paul "Endo" Williamson says that he does not suggest trying it unless you are a professional trainer. I don't think the TAP itself could hurt the horse, it's the fit they through in the process that worries me.