Draining Friendship

One of my best friends is also dealing with depression, and I try to help her the best I can, which usually consists of listening to her because she doen't really feel like she can talk to many people about her problems. The only problem is that when she talks about things she just tends to rant on and on about every little thing that has gone wrong, and often she talks about her problems with her other friends. I always try to listen to her because I know I do the same here on 7 Cups and it helps a lot. I just always feel exhausted after listening to so much negattivity for so long, and it never seems like she resolves anything and just always comes back with more things to complain about and it's draining my energy. Am I a hypocrite for not being able to listen to her problems when I do the same thing on here? Is there a good way to tell her that it's difficult for me to listen to all her negativity without making her feel like a burden or abandoned and adding to her problems and feelings of depression?