I never get the logic of these people. You bring into your family a girl that looks like your dead daughter and then treat her like an interloper...then why bring her in the first place? Why not just mourned her and move on? It's unbelievable that they not have even an ounce of affection for a girl that was with them since young, to the point of selling her off in a marriage. What did she do to deserve that? I know it's a story and they are supposed to be the bad guys (in reference to the MC), but dear lord.
Hopefully we'll get more information as to why they were a bunch a**holes towards her, and that it is not the cliché "you took my daughter's/sister's place" excuse.