She sounds like she truly isn't ready for help or your friendship.
Depression is pervasive and penentrates every aspect of life and living. She cuts people off because in order to keep the status quo the status quo you need to have people continue to feel sorry for you and agree with your position.
It sounds to me like this is more than just ordinary depression but may also be coupled with some type of personality disorder. Many of them come with rejecting others and isolating the person with the condition there by reinforcing the mental montra's of the condition such as no body likes me, everybody hates me when that is not the case.
When people are drowning, safety persons are taught to first keep a distance to the drowning person can get to the place where you can actually help them without having them drown you as you are trying to save them. This means, keep your distance, keep contact limited, make positive deposits and quickly get out of contact. Some of what you say may sink in and penetrate the cloak of rejection covering her.
I always choose positive things from the Bible. That seems to help more than anything else I've tried and this comes from someone who suffered from depression for a really long time.