My "rents got devorced and now my mom is getting remarried and now im stuck w/ an spoiled to death stepsister

uh so my "rents got devorced mom got remarried and now i have to eal with this evil spoled brat stepsister who gets whatever she wants. we always does what she wants to do. e.g. we where going to see a movie and she wanted to see a movie and i had already seen it and i said wait ive already seen this movie and they ( mom abd stepdad) said oh come on * lisa hasent seen it and she really wants to and she is younger then u, take the high road. Well im tired of taking the " high road". she also is supper spoiled e.g. She wanted a pair of shoes annd i wanted some earrings well they bought her the shoes and not me the earrings. they give her $100 a week.... thats what i get a month! ugh i need help she acts so sweet around our rents but around me she is a total jerk. what do i do to get them to relize she is very mean and spoiled and is a brat. HELP!