There's quite a lot at the end that's open to interpretation. You could interpret it as there being something particularly unique about her and her blood/DNA that made her more immune to disease, and so only her descendants ended up surviving. But it doesn't have to be the case - the gene pool gets so mixed after not even that many generations that basically we're all descended from the same person/people going back a thousand years. I do think her importance is more than just guiding Starbuck though, I think it was also in demonstrating to both humans and cylons the importance of their shared genes (i.e. there end up being more hybrids, not just Hera) and it being crucial to the survival of their races.
Another point of interpretation is whether the ending means that the show is set in our distant past, which is pretty much implied. But the way I see it, the whole story is about history going in cycles - "all this has happened before and all this will happen again" - and so it doesn't matter whether it's our past, or the one before that, or our future, or the one after that.
Also regarding whether there is a god, or multiple gods, or even whether there's an intelligent god(s) at all and it's simply fate/the cycle of history that causes everything to happen.
It's one of the things I love about the ending. The character arcs are all resolved, and enough is answered to imply explanations but there's room for lots of different interpretation which feels so much more interesting and involving than trying to explain everything with a single answer.