It is unfortunate that people "play dumb". It becomes a habit, and because people get used to being that way in order to manipulate others, they actually fall out of the practice of THINKING for themselves and become DUMB (poetic justice). So, she no longer PLAYS dumb. She may still possess "intelligence" that she gathers from books or classrooms/seminars/newspapers, etc., but independent thinking/wisdom can no longer be one of her abilities.
"Peace and harmony" is "logical", evil disrupts peace/harmony and is ILLOGICAL, therefore, in order for any type of evil to be committed ("scheming"/manipulating others), a person must not "think" (must not complete their thoughts). It is a shame that people do this to themselves and "play dumb", but it is "poetic justice" because they are unscrupulous.
(don't waste your sorrow and ever feel apologetic to her).