Tapeworm help!!!!!!!!!!!!!!!!!!!!!!!!!!…

hi this question isnt about me so dont call me an idiot but who you can call an idiot is my older sister (22) she bought tapeworm tablet thingies from the internet to get thinner. she is very thin and i dont understand why she would do something this idiotic. she only told this to me her boyfriend and her bestfriend, and also asked us not to tell my parents. im obviously gonna tell and not just gonna ignore this, because i heard tapeworms can kill someone. she is older but her brain is as small as a flee she still thinks she is gonna get thin and doesnt care bout the fact that she may die please help! im only 16 i dont know what to do!!!!!!!