Yeah, I did in my post at the top of the page. It...really distracted me when I played the ending, because that was the first thing I thought when she suggested that. She just showed me how infinite the universe truly was, and it helped me recognize that she was being very, very shortsighted two minutes later.
I don't think you (and some others) are seeing how this paradox has been dissected and explained. Elizabeth says that she can see behind every door and that this one point is where the paths start. The paths of Comstock - Booker. And she explains that the only way Comstock is created is if Booker excepts baptism at this point.
And the biggest catch is that Booker CAN'T make the choice himself. For as soon as he makes a choice the timeline breaks to support each path (baptism/ no baptism). Therefore Elizabeth has to end the loop herself. By doing that she creates a paradox in that loop that if Comstock ever exists Elizabeth will exist and will drown Booker in the same way. So that loop becomes closed.
The Lucete's explain how there are some constants in these timelines. The flipping of the coin is an example of this. Going to that baptism is another constant choice Booker makes. That's why she ends it there.
We can debate that going to a different spot in his path could also effect his desire to get baptized but then Booker wouldn't be the exact same person he is at that exact point in time. And once again the fact that Elizabeth only wants to change the Comstock outcome its understood that she doesn't want to change Booker entirely she just wants to save the world from who he becomes.
From my understanding one of the other reasons that Elizabeth excepts her own death is because she knows what she can become, how strong she can be and how evil some of her choices can be.
And she knows that she isn't supposed to be there. She isn't supposed to exist in that timeline. And that the reason she has powers is because she is currently living in two dimensions.
"The world doesn't like it's pees mixed with its porridge."
And then the fact that once the siphon is destroyed and she becomes all powerful she becomes evil and attacks the "sodom below". She is shown attacking New York City.
So the only way she doesn't become all powerful is if the siphon isn't destroyed and she continues to be a captive in a life that shouldn't exist.
She talks about redemption because she (like Booker) is weighed down with all the bad she is doing to others and wants to be cleansed of that pain.
Just like Booker wants when he gets baptized.
Does that make any more sense?