A Mother's Revenge (1993)

Carol has the perfect family... well, aside from her occasional feuds with her rebellious goth daughter Jill... but her youngest child, Wendy, has straight A's, is a teacher's pet, loves animals--and has recently befriended the school janitor, Mr. Warden. When Wendy goes missing one night, Carol and her husband get a disturbing visit from the cops that sends Carol's sanity into a downward spiral until she can't take it anymore and sets out for revenge.