My girlfriend has social phobia / anxiety disorder. Lately, she is getting worse despite sessions with a psychologist and doctor. She thinks everyone is looking and laughing at her at all times. She can't get out of the house and she is quitting. She does not believe her situation can improve and I don't know how to deal with it. What should I do? How do I help her?
This situation is tricky because you don't want to play too much of a role in her recovery. It's not that you shouldn't help her, but that getting too involved will make her dependent on you (for support, wisdom, motivation) when she really needs to find a way to depend on herself. By developing self-reliance and inner strength, she'll be able to face the paranoid thoughts, examine them, and then either ignore them or challenge them with some good ole fashioned shit-talking.
A second reason you want to be careful is that you don't want to turn into her therapist and turn the relationship into a series of therapy sessions. Not only would that make your interaction very serious and heavy, but it could trap you both in certain roles. Role-playing is sometimes fun and sometimes needed, but too much of it will leave you feeling disconnected from yourself and your partner.
What you can do is make sure she stays in therapy and nurture her independence. How do you nurture independence? By being strong yourself and letting her know that you believe in her and in her ability to be strong. Everyone has the ability to overcome anxiety as long as they're dedicated. I have seen it in friends, in family, and in myself. As long as she sticks to her therapist's plan and pushes herself at a healthy, brisk pace -- not too fast, not too slow -- things will start to improve. Whether she believes her situation can improve or not is irrelevant at this point. That faith will come from persistent effort and seeing results in due time. She can keep her doubts and follow her therapist's advice anyway.