Sarah is a Biblical personality, originally named Sarai, she was the wife of Abraham and bore him a child in his old age, and had a beauty so great that not even national leaders could ignore it.
If you don't believe in Biblical infallibility (or even if you do), then there is a very large case to be made for looking at Sarah's life through a different view than the traditional one. Specifically one can easily make a case for a youthful Sarah, which makes a lot more sense than an elderly one.
Sarah is traditionally seen as this paradox of a figure that is an extremely elderly woman, far too old to bear children, yet at the same time she is also so beautiful that she attracts the attention of national leaders.
The paradox is basically one of traditional translations being held up even when they don't make sense and there are more sensible ways to translate the text. Every instance of Sarah being referred to as old could have also been translated as her husband being old instead¹, in fact this is much more likely due to the fact that the bible always put far more focus on the men in the stories than it did on the women. The bible usually didn't say much about the women at all, just little tidbits here and there.
Genesis chapter 17 is one spot where people like to point and say that it says Sarah is ninety years old. But the only problem is that it does not say that, in context the number is tossed out during a conversation Abraham is having with God about him and Sarai having a child together. Let's examine the text ourselves, this text is from The NIV bible, but appears essentially unchanged in most modern translations.
Abraham fell facedown; he laughed and said to himself, "Will a son be born to a man a hundred years old? Will Sarah bear a child at the age of ninety?"
You see my dear readers, this is what one might refer to as sarcasm. He is laughing when he says it.
We are later given an extremely elderly age of death for Sarah, but many people don't put a lot of faith in the extreme ages assigned to the people living in the first few books of the bible, and there is also the simple possibility that the death age given was an extrapolation derived from the sarcastic age of ninety. The bible normally doesn't give ages for women at all, Sarah even being given an age, or age of death is an exception to the rule, which adds to the case that the death age later in Genesis was an extrapolation.
What is logically required for the story to be taken literally, as written, and including the death age given later in Genesis? Well, what that requires is for Sarah to be possessed of supernatural beauty, appearing as a young woman even as she finished out her 9th decade. Could God have done that? Why certainly, but it wasn't mentioned, and that is a fairly large detail to omit from the story. It is is a continual miracle that lasted for many decades, and it is something that doesn't really have a lot of precedent.
1. In many translations there will be an alternate translation in the footnotes which will instead put the focus on her husband's age rather than hers. More specifically it is several cases of "bearing a child in her husband's old age". This is actually the primary text in some translations.