1) A girl/woman who doesn't like being on the bottom, typically because they don't enjoy being "dominated". I'm also told the bottom hurts more; that might be another reason (although I wouldn't know).
2) A woman who does not want to be submissive to men. It comes from the old Hebrew story of Lilith, who was Adam's first wife. She was forbidden to live
in the Garden of Eden because she refused to be secondary to Adam. The term 'Lilith'
generally has a very negative connotation, and is often
associated with feminism.