You obviously care for her and want her to be happy. Bravo! The world needs all the caring people it can get. I think where it gets tough being around someone like that is when we affirm what they are saying even when we disagree, but remain silent. Do YOU think the world is against her? I doubt it. But when we continue to agree with someone like that, are we being honest or maybe making things worse? I don't think its worth fighting every battle, but a true friend needs to be honest once in a while - or else you're adding fuel to the fire. Its also a matter of is it really your job to make her happy? And how much of your own happiness are you willing to sacrifice for her company? Like I said, don't need to win every discussion, but she needs to respect your need for happiness too. Take care.

Since you have mentioned empathy, maybe try letting her know you know how it feels to have all that anger that ends up spewing negative stuff and then ask how you might be able to help her see the futility of all of that and to try to begin moving in or at least toward a new or different direction. Something is keeping her from lashing out at you, and that might indicate she is actually wanting to be more like you.