She needs a reality check. What she sees in other families is what she WANTS to see. Every family has some drama. Some more than others as some just have drama where as other families are down right dysfunctional.
Howsoever, once we grow up, we have the tools available to us to use and proceed with a happy life. The "tools" your girlfriend lacks is coping skills. She is unable to cope with her emotions.
Your girlfriend needs help. There is a type of therapy that works very well to help people cope with life, rather than turn to destructive behavior. It is called DBT, Dialectical Behavior Therapy. This therapy has a different approach than typical therapy sessions. Typically, a therapy session bleeds out every hurt and disappointment in one's life as they are forced to relive the horrible things of their past. With this DBT treatment, no past issues are dredged up. Rather, one is taught how to deal with today and the future and learn how to cope with life without blaming everything that is wrong on the past.
I am sorry to say, YOU cannot help your girlfriend, she HAS TO WANT IT FOR HERSELF. Because if she does it for anyone other than herself, it is never going to work and will backfire because she is not in the frame of mind to honestly help herself. SHE needs to WANT to get better AND do the WORK.
Otherwise, she is guaranteed to follow the steps of the dysfunctional lifestyle that is crippling her psyche, as it will be her life and her eventual reality.
Sometimes depressed people turn to alcohol to self medicate to escape their badgering busy mind. If she is not drinking now, she may turn to it or perhaps begin taking non-prescribed medications (legal or illegal). I am not saying this to scare you, but unless she deals with her emotions, she is a likely candidate to abuse alcohol and or drugs. Then, there is a whole new set of dysfunctional problems..
Now, about depression: Depression, clinical depression, can be managed with medication. A true clinically depressed person will not get well simply by being around happy people who are trying to cheer them up. Clinical depression is an imbalance in the brain and does not go away with happy surroundings.
Being sad and upset about something is totally different than clinical depression. So, I am unsure what your girlfriend is going through, but you are not qualified to help her as she needs to see a psychiatrist because a psychiatrist can write an RX for anti depressant medication for those who are clinically depressed and the DBT will help her cope with her emotions.