I'm really upset about this

i got scabies just before covid by an ex friend and I cannot seem to get rid of them. Now I think my sister definitely has them but just denies it. she tells me I have no spots so I don't have it. she always gets so angry if i bring it up and i cant ask her without her telling me I'm accusing her. the reason i know she must have it is because she wears my clothes and coats and all our clothes is thrown on the ground then into the wardrobe. she scratches her legs a lot and sometimes her arms too and has told me before she is itchy. I'm at fault and would take full accountability although she always knew i was treating myself and it was too late by the time i could tell her to not wear my things as she would wear it without my permission or she would get angry if i told her. i don't think its fair i get treatment and she doesn't and now at this stage i think all my family will need treatment. its so toxic and sometimes i want to leave home because none of them understand enough or care enough. i just want to be happy again although if i leave home i will have no one how do i get someone to understand. the itch kills me and i always feel a burning sensation on my back and legs. i think i keep getting infested with them because my sister wears my clothes and my mom never washes my coats so its harder for them to go and its also extremely difficult because i have to share a room. my mom says to stop accusing my sister but i just don't know what to do anymore