"You have to make peace with your past." This is the singularity: she had to say goodbye to it, so the angel could carry her across into the next thing. But when the holy man returns to the village and starts crapping his pants, there's going to be the temptation to stop being holy and start being normal. Every second she spends back here, her past is all around her. She has to say goodbye from this side, too.
Imagine if Boomer had done that -- and I think she's a little bit Tory right now, pretending she's a Cylon, playing at it -- on Caprica. If she'd been able to say goodbye to Sharon Valerii, the way Kara needs to say goodbye to Starbuck now. If she'd truly made peace with her past, and let it burn. In Boomer's case, it wouldn't have turned out so well, but it's the same struggle. Guilt and grief are so easily confused: how about forgetting and forgiving? Is forgiveness possible, or are we just pretending to forget and calling that mercy? How do we measure loss? Is a sin of n diameter forgivable, while a sin of 100n is something we gloss over and only pretend to forgive? Where's the line? How can that possibly be how it works? How do you make peace with your past, when all your past is war?
"Why?" Just one word, to a man covered in blood.
"Because that part of you is gone. I told you when I first came aboard this ship that you had changed. I look at you now, I don't see Kara Thrace. I see... an angel, blazing with the light of God. An angel eager to lead her people home."
Downstairs, the villagers are restless indeed. Seelix: "This is bad. This is really bad..." She's not wrong. Neither is Felix: "She can't explain this one away." So then, Karl asks again, is she a Cylon? "Starbuck's racked up more kills than any pilot in the Fleet." To which Pike responds that, yes, Starbuck maybe okay was this ace pilot, but they still don't know who the hell got off the Viper two months ago. Was it a raven? Or a dove?