TS, i understand the agony u facing now believe me i been thru this b4 although is nt exaclty the same.
My advice is same as any other guys is just end the relationship. I know it hurts and may even takes time to heal. For me, i feel she is too young to handle r/s. You may feel she will gradually change her char but she won't.
Ending this r/s i feel is gd for both of u. You both need to move on........