If this trainer insists on gag bits and martingales, I would be more concerned with finding a new trainer...
If your horse's back is injured to the point that the saddle placed in the proper spot is bothering her, then she needs time off until the area is healed completely. Moving the saddle too far forward can cause other issues in the long run.
Ditch the gag, martingale, and the trainer.
All of the horses there are or were polo horses. That might explain the combination of gag and standing martingale.
Its not injured. She's just being weird. Also, when I say far forward I do not mean in the wrong spot, just that if it falls back even a little she would start twitching as if it was irritating her.
To clarify: The running martingale isn't because she NEEDS one. The running martingale is because a standing martingale and breastplate apparently don't work together. Well, OBVIOUSLY don't work together. And this trainer is a firm believer in martingales, even though I don't see the use.
I'm sorry, but ditching my trainer is a little extreme. First of all, she's a wonderful trainer. Despite leaving me to learn my own horse facts (this is why I'm here) she is better than anyone in this area that isn't overpriced and doesn't just say "Get on the horse and ride, get off the horse and leave." Also, these are her horses. If I ditched her, I would have to go to a completely new barn (the closest one being an hour away, one way) and wouldn't even have a chance to ride this horse I have fallen in love with.
Can someone please explain to me how someone could think a gag and standing martingale (or just martingale in general) combination is safer in ANY way shape or form (rider or horse?) I want to know so I can validate her point or yours.