Milka is mentioned a couple of times as giving birth to Nahor's children, e.g.:
... וַיֻּגַּד לְאַבְרָהָם לֵאמֹר הִנֵּה יָלְדָה מִלְכָּה גַם־הִיא בָּנִים לְנָחוֹר אָחִיךָ׃
... Abraham was told, “Milcah too has borne children to your brother Nahor: (Gen 22.20)
וַתֹּאמֶר אֵלָיו בַּת־בְּתוּאֵל אָנֹכִי בֶּן־מִלְכָּה אֲשֶׁר יָלְדָה לְנָחוֹר׃
She replied, “I am the daughter of Bethuel the son of Milkah, whom she bore to Nahor.” (Gen 24.24)
Rivka stresses her father to be Milka's son and not Nechor's.
So who Milka was and why is she important in the Torah?