I think it's important to break it in two. There's the times when you are really listening, and there's the times when you just want to tell them "that's your truth, but not reality!!!

For the first one if you truly want to listen, and take what she says into account. Just quietly nod your head and really listen!!! No phrases are needed except the occasional, I see, I know, and I'm sorry. Anything else will just sound canned.

On the other hand if she is just going into hardcore WAW and is merely yelling at you for the sake of being mean and hurtful. Diffuse, but don't take blame.

I know "you feel" this way, hopefully we can avoid something like this in the future.

Sometimes the best answer is to simply say:

I'm sorry you feel this way, and walk away!!!!

Lets face it often you are just getting baited.

I think the trick is realizing when they are trying to communicate, and when it's just venting. Either way if you're a guy let her vent, and don't try to fix anything. She wants for you to lend her an ear, not give her a hand. i think I'm copyrighting that one smile.