It's a good question; there certainly seem to be some character inconsistencies even if you take into account that there was more of a "role" or purpose for her in LA.
One explanation is that "Orpheus" aired around March, and by then she had really come far in "facing her fear" as she said. "Showtime" aired in January, and in that ep, she put up a wall to keep the Turuk Han out, and as we know, purposefully let that wall drop. So she'd had enough control to put it up and to decide when it would go down at that point, which I imagine took some confidence. Given that, it would make sense that she'd be ready to try re-ensouling Angel by March.
Of course, as you pointed out, the total badassery that she summons in "Orpheus" sort of comes out of nowhere, even if you take all of that into consideration. Maybe it was the fact that she'd done the spell before; that it put her on the map all those years ago. She believed in herself. Certainly, I think Orpheus helped prepare her for what she had to do in "Chosen."