The mother is acting like not her mother? What is wrong with them. Is she not her child?

Turns out they weren't related at all, Im assuming mc was adopted. Also she did not have any of their physical traits like the rest of the kids.

She doesn’t look like them because your appearance changes when you get contract an elemental spirit, and she hasn’t contracted a spirit yet. She’s not the daughter of the stepmother though and wa most likely an illegitimate child and that’s why the stepmother didn’t like her either