Just be careful that she isn't trying to use you as her rescuer and a way out of a troubled relationship. You would have to talk to her more to see where her head is at as far as what she wants from you, she may just need a friend and what better way to win back your ex than to be there for them and be that shoulder to cry on and that "knight in shining armor" so to speak. From what she has said to you it seems she is in an unhealthy relationship and doesn't quite know how to get out of it. What you could do is ask her what her intentions are when she decided to get in touch with you again but don't say it in a way that sounds like she is bothering you. Ask this way, "I'm glad you got in contact with me because you have been heavy on my mind, but I need to know what this means?" She sounds like she really needs a friend right now and doesn't need anything that will confuse the situation even more, so be that friend and that listening ear. Advise her that love shouldn't hurt either physically or mentally and if she feels her boyfriend is abusing her in anyway that is not love and that she deserves better than what she is getting.
Start out being her friend and helping her through this so that you can see if she really wants out or is only saying that she wants out because with most toxic relationships the one doing the abusing or treating the other badly will do anything to keep the other mate around so just be careful that you aren't setting yourself up for more heartbreak. If she truly wants out she will see that you are much more dependable and the right person for her but it will take some time because you don't want to get into a relationship with someone that is still emotionally tied to someone else that is never a good idea. Make sure she can find closure in the relationship if she chooses to leave him so that if she does give you another chance you both can start with a clean slate and truly start over together but it has to start with friendship.