That Whole Munchausen Syndrome by Proxy Plot
Because a horror movie about a woman trying to get revenge on a bunch of former classmates by murdering their kids isn't crazy enough, Ma also tosses in a Munchausen syndrome by proxy side plot for a little extra flavor. (Have I mentioned how insane this movie is yet?) Enter Genie, Sue Anne's long-suffering teenage daughter whom she keeps out of school and locked away in an elaborate cage in their home upstairs, injecting her with all sorts of drugs to keep her docile. Luckily, thanks to a brief interaction with Maggie at the beginning of the film, Genie figures out what her mom really is (f*cking looney toons!) just in time and deals with it in a mature, responsible way (knocking her mom out with a frying pan, as you do).