BOYFRIENDS POSSESSIVE & JEALOUS SISTER HELP

Hey so i’m 16 and my boyfriend has an 8 year old sister. sounds all cute. but she is honestly CRAZY and i feel as though she’s breaking our relationship.

she is so jealous of my relationship with him that she is constantly rude to me. my boyfriend does nothing and i have tried to talk to him but he got defensive of course. it was fine at the start but it’s just too much. we’ve been together for 9 months and i’m so over it. she is so nasty and rude to the point she will say things about my boyfriends ex or tell me my boyfriend is cheating on me. or purposely try and leave me out (she controls her whole family!) she makes nasty comments about me. she will mess with his head whenever he tells her to go.. because she always comes in every two minutes to interfere she will be like oh but you’d let jodie. she sits there and stares at us for literally ages and every time he shows me any sign of affection she will make a comment or purposely hurt herself (like fall over) for attention.. HEEELLPPPP.