This is just my interpretation of the song, I can personally resonate with what she is saying. It seems like she is speaking as herself and addressing the person that hurt her throughout the whole song:
At the beginning she was very in love and infatuated with this person. She loved him deeply and gave him everything in the relationship. She would climb mountains for him. "You kept on thinking you were the only one" could have different meanings. It could mean that he was selfish and he only saw himself and prioritised himself in the relationship, or it could mean that he is a fool to think that she will remain to be dependent on him forever and that to her he is the only one. "Too busy thinking love is a gun." This line could mean that he sees love as a game and anyone who he gets in a relationship with him he disrespects by shooting them with an invisible gun (which is his hurtful words or actions) but his victims don't realise because the bullet moves slowly. This could mean that he is incapable of showing or giving real love to his partners because he could be a narcissist. My interpretation may be a bit confusing sorry. "Hit me like a slow bullet, took me some time to realise it" she doesn't realise that he is not a good person at the beginning. His words and actions hit her like a slow bullet crumbling away at her character, confidence and her essence, and she doesn't realise it at first because her partner is doing it in a non obvious way. He is manipulative.This is how narcissists operate in relationships."I know the end before the story's been told" could mean that she knows the ending of this relationship and it is a positive one for her. The story is her life. This could mean that she will break free from his chains before the story's been told which is the end of her life. She knows she will empower herself and break away from him instead of be a "slave" to him forever. "You're gonna need a bullet proof soul..." She is addressing him when she says this. He thinks that she is naive and will never break free from him but he is wrong. She knows she has been played and manipulated and she will break free and empower herself and this action will hit him like a gun. So he will need a bullet proof soul when she breaks herself free from his games, because the shock of her power will shock him like a bullet. "I came in like a lamb, but I intend to leave like a lion.." She came to the relationship naive, but she intends to break herself free and gain her strength, power and confidence back
This is just my interpretation of the song, I can personally resonate with what she is saying. It seems like she is speaking as herself and addressing the person that hurt her throughout the whole song:
At the beginning she was very in love and infatuated with this person. She loved him deeply and gave him everything in the relationship. She would climb mountains for him. "You kept on thinking you were the only one" could have different meanings. It could mean that he was selfish and he only saw himself and prioritised himself in the relationship, or it could mean that he is a fool to think that she will remain to be dependent on him forever and that to her he is the only one. "Too busy thinking love is a gun." This line could mean that he sees love as a game and anyone who he gets in a relationship with him he disrespects by shooting them with an invisible gun (which is his hurtful words or actions) but his victims don't realise because the bullet moves slowly. This could mean that he is incapable of showing or giving real love to his partners because he could be a narcissist. My interpretation may be a bit confusing sorry. "Hit me like a slow bullet, took me some time to realise it" she doesn't realise that he is not a good person at the beginning. His words and actions hit her like a slow bullet crumbling away at her character, confidence and her essence, and she doesn't realise it at first because her partner is doing it in a non obvious way. He is manipulative.This is how narcissists operate in relationships."I know the end before the story's been told" could mean that she knows the ending of this relationship and it is a positive one for her. The story is her life. This could mean that she will break free from his chains before the story's been told which is the end of her life. She knows she will empower herself and break away from him instead of be a "slave" to him forever. "You're gonna need a bullet proof soul..." She is addressing him when she says this. He thinks that she is naive and will never break free from him but he is wrong. She knows she has been played and manipulated and she will break free and empower herself and this action will hit him like a gun. So he will need a bullet proof soul when she breaks herself free from his games, because the shock of her power will shock him like a bullet. "I came in like a lamb, but I intend to leave like a lion.." She came to the relationship naive, but she intends to break herself free and gain her strength, power and confidence back