It sounds like a one sided relationship, but how can you make her see? That's a tough one. She must be getting something out of this relationship otherwise she wouldn't be with him. Some needs which are being met on some level. You can taker her through a list of things, that she is being used and taken advantage of, that there is a lack of reciprication in the relationship and she is becoming a recluse, but ultimately it is her decision.
You have to accept that some people are just masochistic by nature.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~