Lorna rejoining the Underground was a given before the season even started. Polaris has largely operated on the side of good throughout her entire comic history, and we've known via the writers that these characters are meant to closer and closer to their comic counterparts. Knowing that, Lorna was always going to rejoin the more heroic affiliation. Which is not the Inner Circle. Polaris joined with the Inner Circle because they took a more aggressive stance when it came to helping Mutants, and weren't just smuggling them to safer places like the Underground. Though it looks like the Underground will start taking on a more aggressive stance in these next couple of episodes, so hopefully that sticks around.

And, yes, we've seen Lorna accept what her father did, and that he did that to help Mutants, but that doesn't mean that Lorna should do things the exact same way he did. As I said in the review thread, its important to highlight the differences between Lorna and her father. Last season we got to see what they have in common, and this season we're starting to see how they deviate from one another. The problem more so has to do with the vagueness of Reeva's plan, and what exactly that entails. We don't know exactly what it is, and Lorna is just making assumptions. So I think this plot is a little premature, and think Lorna should have had a more concrete idea of what the Inner Circle was doing before branching out.