So to express here for a moment on the options in front of you:
A Shared Brilliance involves approaching the matter from a theoretical position, working with the Hearts and others in the Circles to spread a much wider understanding of what you're trying to do with them. Extending the metaphor of foundations from bonds, this action would represent Amanda going out and getting people to help her design the house before building it. There would be some experimentation here, but the entire process would be deeply focused on deciphering how what Amanda did worked and then getting groups within the Circles to go through the motions. It's slower, but far more likely to avoid a Hightower situation. Also probably safer.
Beacon of Souls goes at it from the other end, and is very alike to the leap of faith that
@tenchifew described. To further extend the foundations/design metaphor, this options involves effectively throwing bricks and mortar at your foundation until something house-shaped sticks. You have the advantage of Practice to one point or another seeming to just work like this; Potentials aren't involved in the higher thought processes of their work beyond basic intent in most cases. The risk here is that you're not using a known grounding, like Project Insight and the Harmonic Circle have. Backlash is unlikely, and even if it does occur it shouldn't be beyond Amanda's ability to remedy, but if it does occur to that level there will be other consequences.
Basically, you're choosing between high theory or high practical. You're not able to do both. Before any complaints, yes, each option involves the other. But its the focus of your work that you're choosing here. There's also the matter of how much you're trusting the Circles with, which will dictate certain reactions depending on the results of your roll.
@PrimalShadow whilst I appreciate your irritation, the concern is a valid one here given Amanda's mindset and how much she knows about the process of communal Practice. In that it could be considered very similar to prayer, in some ways. She was deeply disturbed by the Lady in Fire Enfolded, even if they're not exactly a cult at this point and don't have any obvious signs of heading there. Existing within the Circles or even leading was always a communal process, even if Amanda's words were deeply respected. LiFE takes that to another level. They're still a product of the social constructs laid down by the Elder First and reinforced by Amanda (and others), but they're also clearly moving into the territory of informed faith. And informed or not, having millions believe in you like that isn't something that Amanda is well equipped to handle. Trust, respect, even some degree of adulation, those are things she knows how to deal with. But faith is different, both in her personal context and also actual fact. She doesn't know how she even wants to start approaching LiFE, the idea of making the organisation larger and therefore even harder to work with...doesn't appeal.
If I didn't make this clear enough from the character piece on the matter last turn, my apologies. Yes, you can look at it from an OoC perspective and see it as you did "They're currently not dangerous, no need to worry.". You're even entirely right at this juncture. But the emotional component isn't to be discounted, especially when you've dedicated a pair of years to Amanda taking the time to get back in touch with herself.
Also, if you hadn't taken the time to look into it? No, probably wouldn't be so much in her thoughts. It's likely to fade from there given time, but right now it's much more present. If it will get the chance to fade is...another matter. And not one that I have any control over, because it revolves around your votes.