One day you will look back on this and have a hard time understanding why you put so much time and energy into this person. There probably won't be an answer, besides naivety.

Hopefully something good can come from this. You now have a much better understanding of what a healthy relationship should or shouldn't be. You will heal and be stronger. One day you will meet someone and be amazed at how effortless the relationship is. You will pinch yourself wondering how you found someone so wonderful. You will breathe a sigh of relief every time you have a minor disagreement and it doesn't end in screaming.

Her mental illness is not her fault, but it is her responsibility.