Depression Supporters Support Group
This community is dedicated to spouses, children, relatives, co-workers and others who are actively supporting someone suffering from depression or other serious mental illness. Depression can bring about intense sadness, melancholia or despair that has advanced to the point of being disruptive, which can have a grave impact on the ability of others trying to help.
A lot of the time, when my wife is at her lowest, she isn't looking for me to say anything at all. She is looking for me to listen when she's finally ready to talk and she wants me to quietly support her until that time comes.
Since she's your daughter and you have a maternal instinct that makes you want to rush in and save her from any pain, as hard as it may be, it sounds like your daughter isn't interested in what you has to say. You could be the best mom in the world, but that won't change the fact that she still sees you as her mom while her sister is more of a peer. It isn't fair, but that's the way it often is. But that doesn't mean she doesn't want you to show up and sit with her, distract her with TV (my wife's favorite) and then when she is ready to talk, you're there to listen and, if specifically asked, offer advice.
Hang in there.
Be patient with her and please try to get a good support system for you!
Big Hug