I get this but it always begs the question; She did have a father and a mother of her own, right? wouldn’t her mother have beed due the honor?
The point is, the genetic mutation marker in the mitochondrial DNA has to match - the source of commonality.
You’re missing the point. The Mitochondrial Eve hypothesis does not state that she’s the first human female. It states that all humans living today are descendants of this particular female. She may very well have had plenty of cousins or siblings that were all equally human, but they bred less prolifically and their progeny has died out.
This purports to show the last common female ancestor, at best.