Thunberg is possessed by a demon. Thats why she was depressed, the demon was denied the ability to do evil by societal conventionaism and the rigors of conformity to decentcy. Once she was allowed and encouraged to rage against decency and let the hate flow , the demon was "all better"and so was she..
Good! Your hate has made you powerful. Now, fulfill your destiny and take your father's place at my side! - Emperor Palpatine- return of the jedi.