How do you make a person who's depressed,has lost all self confidence and self belief believe in themselves?

someone i know has lost faith in their ability to do anything, because of past failures..this person suffers from very low self esteem and what i suspect to be depressive tendencies.she wants do something meaningful, but because the feeling that she can do nothing well is so deeply entrenched in her, she visualises her failure even before starting something..she has little familial support, and yet is financially dependent on them..i have told her that the only way out is for her to start believing in her own potential..and not undermining herself each time..but she tells me that though the desire to do something meaningful exists, she continues to haunted by her failure in the past and so thinks of herself as being incapable of it..what is the way out of this vicious cycle?how can i help her regain confidence in herself and find some meaning in her life?