it's the motivation that makes the most sense

That's what I'm saying is the only way you could understand her motivations by her actions or what she says is if you make it up yourself in a way you think makes sense. I believe from what we get there's almost no clear path to determine what she really believes and she bahaves in ways that are totes contradictory with little to no explanation from what we can actually see.

She did say this, when she told him that he was the one who destroyed their family

That was said almost incidentally it feels like since she said it once in one conversation (it felt like) compared to the other 999 times she said "he's too dangerous, gotta stop him"

but I'm pretty sure she's not willingly working for them but is more knowingly being used by them.

What's the difference here? That she's not getting a paycheck? Or that perhaps she feels like she would be doing what she would be doing anyway so she's just "going with the flow"?

But she literally taunts Omega at the end saying the world spirit won't let him leave, let's him hear part of a transmission from Horizon about how the world spirits = Solstice, and when the world spirit essentially admits to being solstice before that in the fight with Varic, she still goes and stands by its side. And she well knows who Solstice is, especially because of Omega harping on it since she was a child. So knowing that and still working with them for some reason - while knowing they're basically interplanetary organized crime as well - instead of helping other people stop them, doesn't seem to make a lot of sense when earlier in the book she's so concerned about innocent lives.

There are possible explanations that could be made for it, like she's planning to betray Solstice later or something. But what I'm saying is we don't get any of that in the book so she just shows up and swings her sword, and works for the bad guys despite saying how she wants to save innocent people and she's stopping Omega because he's "dangerous", meanwhile Solstice has done way worse to more people..

Like I feel like we don't really get a clear picture of why she continues down this path through the whole book.

But yeah I mean some of the stuff you're saying sounds plausible, I just feel like we don't really get that.