Once she does believe, Emma needs a guide, someone with enough knowledge of Regina, magic and FTL to help her figure out what to do. Gold or BF would be logical choices. It’s time for one or both of them to step up to the plate.
Gold seems to know more about Regina than BF. Her and Gold/Rumple have been going at it for years. I have never seen the BF and Regina interact with each other but it is not to say she knows nothing about her. Its just how trustworthy is Gold? With him you should put the shoe on the other foot and turn the tables on him. In other words use him like he uses other people and manipulate him enought so he has enough slack leftover so he can hang himself.