How can a girl make herself emotionally strong? Strong enough so that the thought of any non-mahram (unmarriageable male) does not even enter her heart, so that her acts of worship (ibadat) can become beautiful.
What do you need to do by becoming so strong that the thought of a non-mahram cannot even enter [your heart]? You don't have to become an angel. Humans are bound to commit sins. Develop the habit of saying Istighfar (seeking forgiveness).