Do not, I repeat, do not use it anymore, or you run the risk not only of causing your horse pain, but of permanently ruining her mouth (or causing her to rear from the pressure--that curb can even break a jaw). It's also time to stop taking advice from Mr. Neighbor....not all "experts" are as they claim to be.
Instead, if you are somehow able to find competent instruction, and a trainer who is willing to work with both your horse and you, that is the avenue I would take. No bit can prevent a horse from running away, but a good rider can prevent a dangerous bolting episode on any horse with any bit. But you have to know how to use the tools appropriately for your horse (and how to choose the correct one).