。
She was very kind to me.
Literal
She [topic-は] me [to-に] very kindly did-for-me.
親切にする ('to treat kindly') uses the na-adjective 親切 in adverbial form (に) with する, while してくれた adds the benefactive nuance — 'she did me the favor of being kind.'
。
She was very kind to me.