Mitochondrial Eve is the most recent common ancestor of our mitochondria. But that only tracks purely mother-to-mother descent; there could be a more recent female common ancestor.

Consider the hypothetical population consisting of two people, whose fathers were both first cousins and whose mothers are second cousins, on their mother's... side.

Their mitochondrial MRCA is their great-great-grandmother on their mother's side, but their MRCA's are their great-grandmother (and great-grandfather) on their father's side.

The entire human family tree is like that, but way, way more complicated.