If I remember correctly, her mom is like way down on the list of concubines, and she's like the 17th kid, who was completely ignored because she wasn't special at all, until her magic woke up.
Thanks for the upload.
It seems people here are having issues remembering that Weiss is not only a powerful mage, a skilled mage, but he is also well practiced dark magic user (a form of magic shunned in this capital city) and a killer. Weiss went into self-exile to Zenis, a city of "villians"...