Are the highlighted words 'painful to,’ ‘let go of,’ and ‘for her son's sake’ correctly used in the text?

Are the highlighted words 'painful to,’ ‘let go of,’ and ‘for her son’s sake’ correctly used in the text? Please enlighten me. Thank you.

Nita handed her son Neil to me and asked me to take care of him. Suddenly, armed men came and took her away. She made a gesture, telling me to escape with the boy. There was nothing I could do but cry for her. What happened to her was very painful to me. Even so, I needed to let go of her for her son’s sake.