From both the TV series and tie-in "Final Five" Comics, we can deduce that Kara "Starbuck" Thrace is a kind of "angel" who is one counter part of two, the other, Pythia (Saul's Mother - Final Five Comic Reveal), whom together make up Aurora, Goddess of the Dawn.
Sometimes, A Great Notion...
The series, like a lot of science fiction, features a spectrum of characters with metaphysical properties to convey the sense that anything is possible and everyone has "a role to play". There are then different "types" of phenomenology to help play into the notion that there IS "something" bigger than the self leading the characters. None have all the power and then add an air of mystery. Battlestar [re-imaged] is basically a Space Opera so of course it leans heavy on "God" and 'apotheosis'.
Head Six and Baltar are other kinds of angels, but more specifically seem like guides and "messengers". It's unclear if they are solely astral projected, but Starbuck clearly is more corporeal prior to disappearance.
The Prequel TV Show Caprica further fed into this by fixating on [technological] apotheosis. Zoe, for instance becomes essentially a holy trinity, as she manifest into a holographic spirit in V-World, The Robot Centurion/"Skin Job", and then Messenger Zoe also exists to help guide the original Zoe and the Holographic Zoe. Eventually Zoe and Tamara (Joseph Adama's Daughter also killed in the bomb blast) somehow can "cheat" death in V-World seemingly because their holographic counterparts are apart the originals' souls and therefor can not die within the holographic space. They become "The Avenging Angels" in the New Caprica City Game.
Lacy: “Trinity, that's what you are."
The reason this additional information is important is because,
Baltar and Caprica Six also were in a blast like Zoe (bomb on train) and it is their 3 images that are represented by the Messengers, even though, like Zoe, we know the image of the messengers can exist prior to the corporeal counterpart's death or birth. Head/Messenger Six helped aid Michael Tigh (Saul's father) and Pythia on Kobolt when Pythia was imprisoned. (see first comic image above)
Because Starbuck's Death has "3" variations. Lee says, he sees her Viper explode in the Nebula. Starbuck claims she went through, went to Earth, and came back, and then the revelation that her burned body and viper were still recognizable and somewhat in tact when the characters visit the first earth in season 4. The Nebula, a black hole, conveys a notion of playing with space-time, but the fact there are 3 variations in events could feed back into "trinity" allegory.
When we look at the life of Zoe, we can gather she was brilliant child whom was to help [re] create centurions in the Caprica/12 Colony pre-fall era, as she was "drawing" them as child. This puts her in line with Hera and her messenger six art and musical notations (furthered by Starbuck), and when you see how Battlestar ends for Hera, one can see a cycle full-filled in the sense that Zoe never got the love & devotion of her parents she deserved, instead she joined a monotheist cult and died for it, and her father Daniel (same name as Kara's father and the missing #7 that the Cavil's destroyed) continued to use her knowledge for prophet gains post Zoe's death. Hera is able to spend the remainder of her life with her parents without technology and among simple indigenous Earth 2 peoples. Like Starbuck & Pythia, these two characters, are like counterparts in space-time.
Note: Always thought it was curious that Zoe and Hera looked like they could be Caprica 6's and Baltar's children, more than either of the childrens' biological parents, especially when Baltar and Caprica are prophesied to play parental/guardian roles in the final deadly sequence that parallels the Opera House sequence.