Someone gave a speech long time ago about how:

The husband takes the anger out on the wife; the wife takes it out on the kids; the kids take it out on the dog; and the dog takes it out on the yard.

What do you do when an abused person is so stressed out from her abusive relationship that she takes it out on you to the point she is abusive? Where do you draw the line and say, "I want to be understanding, but there is no excuse for your behavior?"

And how do you explain the behavior when someone abuses you mimicing the very abuse she is receiving from her partner? He is controlling towards her; and she is controlling towards you. He puts her down to make her feel bad about herself and she does the same to you.

P.S. This may not be purely a "coping" issue since she was kind of toxic prior to being in an abusive relationship.