In that moment,that very moment she realized something she never knew before. She realized she could hurt the people she cared most about.
She grew up innocent. She was a people pleaser. She tried her best to make others happy. As she grew up she started to notice that things she normally did to make others happy, made her miserable. They were miserable, continuing a trail of unhappiness and no completeness in her soul. She realized doing things for others made her hurt. However, instead of changing what she did she continued.

Her theory-> Continue to keep my space right and perfect. people will not have to worry about me. They can go on their way, and not get angry.

Continuing on with life things got complicated, quicker and easier. She was made fun of, beat up, and even emotionally killed to make others happy.
She then met this boy. He was all she ever wanted. He treated her the way she had never been treated; coming from a broken home, she was never paid attention to, and never really given the emotional support she needed. She loved him with all her heart. They had a couple bumps across their relationship, but they made it through it. They went places and did the unimaginable together. She wanted her life to be with him. He was the light in her life, continuing to push his warmth into her heart. She did not realize it but he was broken too. The reason to as why she didn't see this is because when they were together they were one, the were their own whole.
Then one day they had the worst argument they could have ever had. However this argument was different, it could have lead to the end of them. It lasted for 3 days. A full 3 days!!! She was depressed in these days, however , of course she had those few friends who helped her feel better, but she still wasn't whole.
AND IN THAT MOMENT. That very moment, she realized she had hurt him and needed to fix it. She pushed for their relationship and he did too. She then realized that even in the moment she hurt him and he hurt her, it was all worth it. In that moment all the pain she had ever endured, was worth it. All the fights and the arguments that had lead up to that one event was worth it.
She then knew she would spend the rest of her life with that boy, because not only did they survive through the good times but also the bad, bloody, ruthlessly horrible times.