First of all, Lilith doesn't show up until the third century, so it makes sense that the she doesn't show up in the Pentateuch. But there was a whole season of Supernatural dedicated to her, so at least there's that.
She may not have been offically added to Jewish mythology until the third century, but it was taken from another source, lie most of the Jewish myths, so the story character was probably around much longer.
But yeah, because the story of Lilith chronologically comes before Eve, many assume that her story was written before the story of Eve. If it were, then it was dropped for several centuries, only to be kind of added back in later, but I did a quick search and there does nto seem to be any evidence of that.
@snytiger6 And of course a lot of that is based on where you date the Pentateuch in the first place. Some scholars put J/E around the first Babylonian incursion into Israel, and the P after the fall of Judah... Other scholars date it sometime right after the Babylonian captivity, and now Persian captivity. In either case, Lilith, just like Adam and Eve, have very Babylonian similarities.
Of course she is mentioned in Isaiah, which scholars have pretty much agreed was written during Babylonian captivity... So I guess it's safe to say she was known by the Hebrews (at least the more educated ones). So yah, she had a rep even back then.
And then later, in Supernatural, she became the final seal (66) that had to be broken to let Lucifer out of his cage.
I like asking christians about Lilith and seeing the deer in headlights look from them. I mean, same god, same dude, same garden, 1st wife...can't understand why it's not included. Would help them in the whole Earth population issue while Adam and Eve were on vacation at Sandles Resort and Arboretum