How to help when it feels like you can't do anything.

As someone who has been on both sides of this topic, I would say all you can do is to just continue being supportive. Also be sure to not suggest/do anything unrealistic. Sadly there are just some things in life that cannot be solved with help and only time will tell how things will move forward. Be sure that she never gives up hope to cross to the light on the other side of this long dark tunnel she is currently walking through. It may seem never ending but as long as she pushes forward all will be well. I realize this may sound like the worst advice ever, but trust me when I say I have been there and there really isn't much that can be done.