Błędnie: She's been acting as if she were unsane- all she has done so far can bring about lots of trouble. Poprawnie: She's been acting as if she were insane- all she has done so far can bring about lots of trouble.
Antonim przymiotnika "sane" ('zdrowy psychicznie', 'rozsądny')tworzymy dodając przedrostek "in-", nie "un-". "Insane" oznacza 'szalony', 'obłąkany', 'chory umysłowo'.