Don't ask her any questions she can answer with a yes or no.
As someone said correctly, one can not be dx'd accurately on the internet, but I would question as to whether she has a developmental disability of some sort. She doesn't seem to grasp some of the concepts you share with her. If she's dev. disabled and depressed, that would be a double whammy.

IDK maybe talk about a girl's night out, and then primp and clean her and yourselves as a group for the event? See how she responds to that. Complimenting her on good actions should result in her desire to do more of them. If not, then she probably does need professional help.