Common signs can include excessive sadness, withdrawal from friends and family. For example, she might stop going to social events she used to love. Also, changes in eating and sleeping patterns are often seen, like eating too much or too little, sleeping all day or having insomnia.
No. Such a topic involves inappropriate and private behavior that is not suitable for public discussion, especially in the context of a classroom which should be a place for learning and appropriate behavior.
Encourage her to engage in activities she used to like. Maybe she liked dancing. Sign her up for a dance class or just have a little dance session at home. Also, make sure she has a healthy lifestyle. Help her with having regular meals and proper sleep. And most importantly, let her know that she is not alone and that you are there for her no matter what.
It could be many characters. For example, in 'The Hunger Games', Katniss Everdeen is a teenage girl hero. She volunteers to take her sister's place in the deadly Hunger Games, showing great courage and resourcefulness in the fight for survival against other tributes and the Capitol's tyranny.