family betrayal

so my step sisters are a year and two years younger then me but we’re very close. suddenly they went and told my step mother that i do drugs and have had sex and whatnot and she told my father who told my grandparents whom i live with. they asked me and i told them i tried weed a few times and i never had sex just played around. my sisters also decided to start making stuff up and saying that i was pregnant and went to a clinic for an abortion. now this weekend i have to sit down with my whole family until we finish arguing or something. its going to be horrible. i never thought my sisters would do something like that to me just because theyre sick of hearing their mother complain about them being little goth kids. my step mom is really hardcore christian and now she thinks im this horrible person. she also has decided to dream up that my father either killed my mother or my mother killed herself and shes getting into my mothers records and i think thats none of her business. anyways this week is going to be hell and i really dont want to spend my saturday with my family questioning me about what i have and havnt done. UGH!