You say she always fought dirty and is very determined to get what she wants. She will not change. Fighting dirty is what she knows how to do and, even though it is not effective, it is still all she knows. If she is so determined she will do whatever it takes to reach her goal and not let anything stand in her way - including you.

If you stay with her be prepared for her to be mean to you, be ruthless in her actions to reach her goal and possibly decide you are in her way and toss you to the side. She sounds very selfish. You will not change her.