Her name is Becky Smith. She is your half sister from your father's new family and she is in same school like you and don't like you as she have something else her ear rather then the real truth about her mother cheating with her friend's husband and made them divorce and her husband start new family with her after he had a kid with his old wife tho he is paying child support monthly. Tho your half sister don't like you that much

She was walking but fall and got knee hurt and crying and you saw her walking and she was angry (Becky): "Ouch ouch! My knee hurt that damn shoes are reason I slip, It isn't my fault"