She may be a wonderful person that would be a good girl friend for you but at this time she is not available. She may continue to stay in her current unhealthy relationship or may later dump him but it is not in your control and it doesn't seem logical to me to wait and see if she will become available.

I think you need to develop more friendships with other girls and perhaps one might be special or maybe not but dating different people may turn out to be enjoyable and worthwhile.