But they (on the Galactica) said the atmosphere would crush her, so if she ejected, she would probably die.
Well, I've always been led to believe the inner pressure would explode you instantly in space, yet BSG gave the Tyrol family a few seconds leeway... so maybe Starbuck had a few seconds to be snatched by the Heavy Raider and end up sick but not dead. Also, she's in a pressure suit, which could buy her a little time. Not to mention, Raiders have jump drives: they could grab her just about instantly if they wanted to.
Lastly, I don't think she was at crush depth yet--she wasn't THAT far below Apollo, and maybe even higher than the Raider (which I think is real and Lee saw it) and it didn't seem like she imploded, it seemed like her Viper exploded from the damage it took. I think the damage to her windshield was the catalyst for her ship being torn apart. Now, her suit wouldn't have the same strength as her ship, but at least if the ship wasn't crushed, there's a chance she was high enough in the atmosphere to survive for a moment too.
Her being a Cylon certainly would explain her visions etc.--Cylons do seem to have quite the spiritual side--but it's not the only explanation.
But even if Leoben does rescue her physically... that doesn't mean she's NOT a Cylon