How to deal with someone who's being negative towards her own family?

She never appreciates what her parents have ever done for her. Thinks the family treats her like an outsider. Tells everyone that her parents forbid her from having friends, boyfriend etc. It's like she always has some kind of negative perception on people around her especially her own family. At the age of 27, she doesn't even know how to work things right but when taught (chores etc.), she never learns from it. In fact, she even gets furious whenever people try to teach her to do sth right. She lies a lot which makes thing even worse. She's undergoing therapy. It's been for years but I think it doesn't work at all and I feel like going with her to the hospital only that the doctor won't allow me into the room during the session. I really wanna know how I can help her and make her into a better person for her own sake. I need a good approach since I'm just 21 and she strongly believes that I'm too young to give advice to her. Also she would feel like I'm looking down on her by doing so.