"I wanted to break you, make you a monster like the one you left inside of me" seems to implied that her ex had made her filled with rage via neglection and suffering. "All the holes", my thought, is about that ex damaged and changed her via mentality over time, even the "you don't wanna see all the holes" really saying a lot. But she seem to have a lot of courage to say we are done via "Loved you now I'm on my own" so she can finally be free from the suffering since the ex doesn't seem to change for the better so she don't have to. Even the most unconditional love can be turned into hatred. If it's someone you really care and love but seem to care less about you and yet staying in relationship, you don't need to stay anymore with that person, it's better to find someone who actually give a damn about you.
