If she is not interested in the relationship for any reason (which is evident from the fact that she has broke up and now into the relationship with your friend) you should not compel her for the same. See, relationship is something which should come naturally and not by compulsion or by pushing yourself on some one. The fact that you still love her cannot bring her back to you. Even if she comes back, you cannot trust her for similar repetition at any point of life. Best thing is end up this and move on.