the best thing is to offer personal advice to both, in the sense that you make each one understand what the other one feels. don't take sides, but offer an impartial referee stance. I have had this problem with my friends who broke up, and regarded me as a middle man to vent to.

say 'well, so and so is acting this way because she is feeling this'

and vice versa and so and so.. i am sorry if this doesn't help, but it is a very good way of not choosing sides, but acting as a mediator to help each side 'wear the other shoe' if that makes sense. xx