You are correct; she is immature. A child often does things without recognizing that there sre consequences. Continuing this would just end in pain for you  and of her lack of understanding for the pain she causes you. You made maximum effort, you tried so now is the moment when you should drop out of this game and look for someone more mature. Close the door and don't look back even if she calls you; get on with your life. You have good character that someone fortunate will appreciate.